Step 1: Preheat your oven to 3750F (1900C). Lightly grease a 9-inch pie plate or a similar oven-safe dish.
Step 2: In a medium skillet, heat the olive oil over medium heat. Add the chopped onion and cook until softened, about 3-5 minutes. Add the minced garlic and cook for another minute until fragrant.
Step 3: Remove the skillet from heat and let it cool slightly. In a large mixing bowl, combine the squeezed dry spinach, cooked onion and garlic, cottage cheese, and shredded cheddar cheese.
Step 4: In a separate bowl, whisk together the eggs, milk, salt, black pepper, and optional nutmeg until well combined.
Step 5: Pour the egg mixture over the spinach and cottage cheese mixture in the large bowl. Stir gently until all ingredients are evenly distributed.
Step 6: Pour the entire mixture into the prepared pie plate. Spread it evenly.
Step 7: Bake for 35-45 minutes, or until the quiche is set and lightly golden brown on top. A knife inserted into the center should come out clean, or the center should have only a slight jiggle.
Step 8: Remove from the oven and let the quiche cool for 10-15 minutes before slicing and serving. This resting time is crucial for the quiche to fully set.