To make oat cups, mix together oats, parmesan cheese, chilli flakes, oregano, parsley, rosemary, salt, crushed peppercorns, egg white and 2 tablespoons water in a bowl to form a soft dough.
Preheat oven to 180° C. Grease 12 tart moulds with some olive oil.
Line the moulds with the dough. Prick all over with a fork place them in the preheated oven and bake for 10-15 minutes. Remove from heat, cool and demould.
Place them on a baking tray, place the tray in the preheated oven and bake for another 5-8 minutes. Remove from heat and cool completely.
To make filling, heat olive oil in a non-stick pan. Add garlic and sauté till golden brown. Add onion and sauté till translucent. Add thyme and mix well.
Add mushrooms and sauté for 1minute. Add walnuts, salt and crushed peppercorns and mix well.
Add cheese, mix well and fill the oat cups with this mixture.