Bento filler: Cherry tomato and leftover vegetable gratin cup


This vegetable gratin in a cup is a great way to use up leftover vegetables in a tasty way. It only takes a few minutes to assemble too. The only thing you should have are the cherry tomatoes, which make their own sauce in a way. Otherwise you can use any cooked or frozen vegetables you have on hand. Here I’ve used some leftover zucchini and frozen carrot and peas. You could use the ever popular sweet pepper and onion confit too.

The ‘sauce’ used is mayonnaise. Cooking with mayonnaise may seem a bit odd, but it works very well. It’s a very popular all-around sauce in Japanese home cooking. Cooked mayonnaise sauce tastes very nice when cold, making it very suited to bento dishes. I have used a ‘light’ mayonnaise here to halve the calories (50 calories per tablespoon, instead of about 100 for regular mayo), and added a little pesto from a jar to make it even tastier. I seem to always have jars of sauces spreads and pestos and so on around in the fridge - if you do too, try experimenting with them!

You do need a toaster oven to cook them up fast, but for serious bento makers this is a really handy piece of kitchen equipment to have (see essential bento making supplies).

This is a lacto-ovo-vegetarian recipe. To turn this into a vegan one use a non-egg mayonnaise substitute and omit the cheese. You can up the nutrients by adding chopped up leftover meat, more cheese, and so on.

Recipe: Cherry tomato and leftover vegetable gratin cup

For each cup:

  • 2 to 4 cherry tomatoes, quartered or halved depending on how big they are
  • 1 heaping Tbs. chopped up leftover or frozen vegetables
  • 1 Tbs. light or regular mayonnaise
  • 1 tsp. pesto
  • 1 tsp. or so grated cheese
  • Dried basil or oregano or Italian Herb mix

Equipment needed: toaster oven, cupcake cup (aluminum or silicone)

Mix together the mayonnaise and pesto (you can leave the pesto out if you like). Mix in the chopped vegetables, and then the halved or quartered tomatoes.

Put the mixture into a cupcake cup. Top with cheese, and a little dried basil or oregano. Cook in a toaster oven for about 6 minutes, until bubbly and a bit browned on top.

Cool before putting into bento box.

If you don’t have a toaster oven, you can make this in a regular oven at 200°C / 400°F for about 10 minutes. But making just one in a big oven isn’t too efficient energy-wise, so…this might give you a reason to get a toaster oven if you don’t have one!

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monokuro boo

well, because the rice is in squares, you can design them to look like monokuro boo! :D

just a suggestion


oh wait… oops i thought i was on the square shaped rice page…

sorry! >__<

I like these cups. It’s a

I like these cups. It’s a very clever way to use leftovers.


These cups look delicious! I was really disappointed to read that you need to include the tomatoes because of their juicyness, because I cannot stand tomatoes. Is there another vegetable that you might suggest that would produce a similar effect? Or, failing that, would it ruin it too much to just leave out the tomato?

Sure, you can leave out

Sure, you can leave out tomatoes - it will taste different, but should still be good. You may want to add a tad more mayonnaise in that case.

I thought silicone cups

I thought silicone cups could not go in the toaster oven, just the conventional one?

Unless your toaster oven

Unless your toaster oven gets extremely hot (over 500 degrees F or 250 C) they should be fine, but check the packaging…the ones I have say they are safe up to 265 C.

can you substitute anything

can you substitute anything for the mayonaise as I can’t stand the stuff


Just an idea for people wanting to cook them in a conventional oven. You could make a whole batch of them and then freeze them. When you want to use one just pop it in the microwave to defrost and give a nice texture. If I find something to substitute the mayo I’m going to amke them and try freezing them. It should work. That would also make for speedy bento prep.

I guess I could always swap

I guess I could always swap the mayo for a pasta sauce or something

Mayonaise substitute

In italy we have besciamella, a sauce cooked with butter, flour and milk. This is always used to make gratins, lasagne and is easily found in all foodshops.

A simple recipe for doing that at home is:

50 grams butter 50 grams white flour 500 ml milk salt, pepper and nutmeg

Put in a pan the milk and heat it. In another pan, make the butter melt, then add the flour and mix well. When you have a smooth cream, add the heated milk, and salt, pepper, nutmeg to your taste. Cover with lid and stir keeping the cream without lumps. Keep gently boiling until it becomes creamy and thick.

Hope this helps, thanks for the great idea! ;)

I see that some people have

I see that some people have a problem with the mayonnaise. Of course you can use any other kind of sauce that you like - it’s just that mayo is something many people already have on hand and is handy to use. Bechamel or white sauce would be the traditional sauce to use for a gratin, but many places don’t have it ready-made in cans or bottles etc. Anyway, it’s not a problem in any way to adjust and adapt a recipe!



Re: Bento filler: Cherry tomato and leftover vegetable ...

This recipe makes a great spinach gratin!!!

Re: Bento filler: Cherry tomato and leftover vegetable ...

Maki, should something different be done if they are cooked in a conventional oven? I don't have a toaster oven, because I don't have much counter space. These look really tasty and I want to try them!

Re: Bento filler: Cherry tomato and leftover vegetable ...

i tried this tonight with broccoli, cherry tomatos, peas, and parmesan (with a heavy sprinkling of basil and oregano, as well as some garlic powder) - DELISH! can't wait to use these in my bentos. thanks so much for the great recipe maki!

Re: Bento filler: Cherry tomato and leftover vegetable ...

I saw this when I was poking through the archives. I made some last night and I love it. I don't use pesto and didn't want to spend seven dollars on a jar that'll sit unused in the fridge, so I substituted a pesto seasoning pack from the grocery store. Far as I can tell, it turned out fine. I'll be making more for lunch tomorrow!

Re: Bento filler: Cherry tomato and leftover vegetable ...

I've found creme fraiche or cream cheese is just as tasty as mayonnaise.


This is a great way to use leftovers! :D. However, I wonder what this tastes like baked in the oven covered in Bashamel sauce instead of mayo! :O. Bashamel sauce is a white flour sauce thingy lol. it's hard to describe. its used for baked pastas/lasagnas. Mmmm this and some grated cheese would be AWESOME!!

Re: Bento filler: Cherry tomato and leftover vegetable ...

I just made a few of these using normal tomatoes, mushroom, potato and leek - leftover vegetables from my kitchen. It tastes pretty good, except maybe next time I'll use a bechamel sauce or creme fraiche instead because the mayonnaise taste was quite overpowering, and I don't particularly like mayonnaise.

Re: Bento filler: Cherry tomato and leftover vegetable ...


This is my first time entering this site~
and this recipe looks yummy~ and am gonna try cooking it~^^ and...I was wondering
what if u cook it in a microwave? is that ok too?

Re: Bento filler: Cherry tomato and leftover vegetable ...

A microwave will not give the same result. You wouldn't get the nice browning on top, which is what makes this good.

Freezing them?

I'm just about to try your recipe^^ and I was wondering, can you freeze them? I'm a newbie and I don't really know what you're not suppose to freeze. Anyway, it looks sooo tasty!!!

Re: Freezing them?

Whenever I put a recipe here, if it can be successfully frozen I usually say so. This could try freezing it, but it's so easy to put together at the last minute that I don't bother to usually. Plus, the tomato may get a bit too watery before it can bake (which evaporates the excess moisture).

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