Make the tofu sauce. Beat the egg into a bowl and stir in the mayonnaise, salt, and pepper. Add the tofu and crumble as you mix it in.
Scrape off the hard parts of the asparagus skin and cut into 4 cm pieces. Remove the root from the shimeji mushrooms and shred. Thinly slice the onion.
Break up the canned mackerel a bit and place in a casserole dish with the sauce from the tin as well.
Top with the asparagus, shimeji mushrooms, and onion from Step 2.
Pour over the tofu sauce from Step 1 and bake in a 230°C oven, or in the toaster oven for 15-20 minutes.
For a yamaimo yam version, see Recipe ID: 2417461.
Story Behind this Recipe
I heard that canned mackerel has good properties for dieting, so I wanted to make something healthy and with a lot of volume. So I made this tofu gratin.
You don't need to parboil the vegetables, just mix into the tofu sauce. You can use any vegetables you want but the onion will neutralize odors from the fish and increase the flavor, so it's required! You can use canned tuna too. Add rice to make a pilaf-type dish. Or just use vegetables for a delicious vegetarian gratin.