I went to the farmer's market and picked out all the ones shaped badly and/or whose skin was falling off for a total of 12 large and small onions for just 150 yen!
Thinly slice every single onion and microwave half the amount at a time in a 500W microwave, uncovered, for 5 minutes. Then move to the frying pan.
Swirl in the olive oil and sauté over medium heat. The photo shows what they look like after 10 minutes.
This is after 25 minutes. They're starting to color. From this point on they will burn easily, so don't take your eyes off them while cooking.
Here they are after 40 minutes. Good job! If they have completely changed color at this point, they're all done.
Once they have cooled down, wrap up small quantities and then place in a ziplock bag and store in the freezer. This time I put in 2 onion gratin soup servings (30 g) in each ziplock bag for 18 portions.
Add some to onion gratin soup.
They can also be used in bread with browned onions and bacon.
Story Behind this Recipe
When I was a child, my mother always made onion gratin soup using a stock of onions she kept in the freezer. Whether you want to make a lot or just a little, the procedure is the same.
Microwaving them makes them tender and decreases the volume. This also makes them easier to stir and decreases the cooking time. Once they begin to change color, keep your eye on them while stirring so they don't burn.