Make sure you press your tofu, or it may be too watery and make your filling runny. You can find instructions for that here.

Preheat oven to 375° F.

Mix one tablespoon of the lemon juice with the avocado oil and tamari and blend into a marinate. Submerge the mushroom caps into the marinade and cover them with marinade on all sides.

Place mushroom caps in a baking dish or oven pan and roast for about 15 minutes, or just until they start to become tender. Brush the edges with pan juices to keep the mushroom moist.

Meanwhile, make your stuffing. First, take your spinach and quickly steam it just until it is wilted. Drain the spinach and pat with a towel. You can also substitute 1 cup drained frozen spinach in a pinch.

In a medium mixing bowl, mix the miso, mayonnaise, and lemon juice into a paste, and add the spinach, stirring into a spinach paste of sorts. Cut your tofu into small chunks, the size of almonds more or less, and stir into the spinach paste.

Mash the tofu a little until you get a stuffing with chunks of tofu that holds together fairly well.When the mushrooms are ready, pile a generous mound of stuffing on top of each mushroom. Sprinkle some sesame seed on each mushroom, and return to the oven.

Bake the mushrooms for another 25-30 minutes, until the mixture is browned, and cooked all the way through. The mayonnaise in the stuffing should cause a slight soufflé effect, and be a little bit like "dynamite" that you get at the sushi bar.

Enjoy immediately with a side of grains or vegetables, or save for a cold lunch entree with a green salad.