Heat oil in a non-stick pan over medium-low heat. Add diced garlic and fry for 2-3 minutes. Add turmeric powder, chopped spinach and mushrooms; mix well and cook uncovered over medium heat until all the liquid is absorbed.
Crack the eggs into a bowl, stir gently with a fork until well-beaten. Add salt, black pepper, dried thyme, 1/2 cup shredded mozzarella cheese and ricotta cheese; mix well.
Add spinach mixture and combine well.
Preheat the oven to 370 degrees F. Coat the bottom and sides of a 8x8-inch baking dish with the oil. Pour mixture into the baking dish. Place on the middle rack of the oven and bake until frittata is puffy and golden. Remove from the oven and sprinkle the remaining mozzarella cheese all over the frittata. Return the frittata to the oven and bake until cheese is melted.
Serve Spinach Ricotta Frittata warm or cold with toasted bread.