How to make
Melt the butter with the olive oil in a pan and braise the onions. Add the chopped zucchini, celery, mushrooms and green beans.
Saute 8-10 min. Beat the eggs with the mascarpone, thyme, basil, season with salt and black pepper.
Add the tuna to the zucchini mixture, finally add the shrimp as well.
Pour the egg mixture on top and cook 5 min. Put the frittata on a grill and bake until slightly browned. Serve right away.