I used the tempeh sausage crumbles recipe from Vegan with a Vengeance and modified it for the stuffing.

Ingredients-
14-15 large white mushrooms (or use five portobellos)
1 tbsp olive oil
8 oz (I packet) tempeh
* can be substituted with Indian cottage cheese/paneer, Mexican queso fresco, or even cooked beans.
1 tsp fennel seeds
1 tsp pepper flakes
1 tsp dry basil
1 tsp dry oregano
2 tbsp soy sauce or tamari
2 tbsp lime juice
1/2 cup finely chopped parsley (about 1 bunch)
1/4 cup nutritional yeast (or use your favorite cheese)
salt to taste

- Pre-heat the oven to 350 degrees.
- Remove the stems from the mushrooms and chop them up.
- Break the tempeh into pieces, cover with water in a microwave safe bowl and steam for 4-5 minutes, until most of the water is absorbed. Or steam conventionally for about ten minutes. Drain the water and crumble the tempeh.
- Heat oil in a saute pan. Add the chopped stems and saute until they release water.
- Add tempeh, spices, soy sauce, lime juice and saute for five minutes until browned.
- Turn off the heat and add the parsley and nutritional yeast. Mix well. Add salt if needed.
- Stuff the mushrooms with the mixture and place on a greased baking sheet.
- Bake for 20-25 minutes.

Garnish with more parsley and serve.