Cut onion into small bits and briefly sauté in olive oil using a frying pan.
Slice the mushrooms, add to the pan, and continue sautéing for a few.
Toss oats into pan, top it off with the veggie broth, and bring to a boil. Simmer over low heat until desired (thickened) consistency is reached.
Add your baby spinach and let it briefly simmer until spinach has visibly wilted.
Crumble up feta cheese and fold into the mixture until nicely melted. Season to taste with salt, black pepper, and nutmeg.