This is a very simple and easy vegan filling for onigiri and can be made in just 10 minutes. The secret to this great filling is using Japanese soy sauce! Any mushrooms are great for this recipe and here we have using crimini mushrooms.
Mushrooms release a lot of liquid and so the key to this recipe is to ensure that the liquids are evaporated or cooked down. It is crucial that the mushrooms are not soggy as this would make the onigiri rice very wet and your onigiri would be soggy when you eat it.
Ingredients (makes 8 onigiri)
2 handfuls crimini mushrooms, or any mushrooms you prefer
1 shallot, finely chopped
1 tablespoon aromatic sesame oil
1/2 tablespoon dark colored soy sauce (Japanese style)
1/2 tablespoon light colored soy sauce (Japanese style)
1 clove fresh garlic, minced finely
1 teaspoon mirin or sake (optional)
Finely chop the mushrooms. Mushooms will shrink after cooking but we still prefer minced mushooms so that it's easier to put inside the onigiri.
Sautee the shallots in sesame oil and add the chopped mushrooms into the pan in moderate heat.
Add the minced garlic to the mushoom miixture.
Add mirin into the mixture and turn the heat higher. Add the soy sauces and cook until mushrooms have released most of their liquids.
Cook over medium heat for another 5-10 minutes (or until reduction happens and liquids are mostly absorbed)