Preheat oven to 180 Celsius (350 Fahrenheit).
Roast the walnuts for 10 minutes and remove.
Increase oven to 200 Celsius (400 Fahrenheit).
Clean the mushroom and remove the stems.
Chop the stems.
Sauté the onion and stems in the olive oil (2 minutes).
Add the garlic and cook until onion is translucent.
Add the thyme and remove from the heat.
Combine the ricotta, honey, cooled walnuts, 2 tbsp of bread crumbs, nutmeg, and onion mixture.
Season liberally to taste with salt & pepper.
Fold together, and fill mushrooms until even with the top of the mushroom.
Combine remaining bread crumbs and parmesan and a little more salt and pepper.
Sprinkle this mixture over the top of the mushrooms
Bake at 200 Celsius (400 Fahrenheit for 20 minutes).