In a large skillet, heat the olive oil or butter over medium heat. Once hot, stir in the minced garlic and sauté for about a minute until fragrant.
Next, add the sliced mushrooms to the pan and cook them for 3-4 minutes until they become tender and slightly browned. Toss in the fresh spinach and cook until it wilts, about another minute.
While the vegetables are cooking, crack the eggs into a bowl. Add the milk or cream, salt, and pepper, then whisk everything together until well combined.
Pour the egg mixture directly into the skillet over the sautéed vegetables. Cook gently, using a spatula to continuously stir the eggs, until they are softly scrambled and just set, about 2-3 minutes.
If using, sprinkle the shredded cheese over the top during the last minute of cooking. Gently fold it into the scramble until melted. Remove from heat and garnish with fresh herbs before serving.