01 - Whisk together flour and salt in a mixing bowl. Create a well in the center, then add eggs and half the milk. Whisk until smooth before gradually incorporating remaining milk and melted butter. The batter should have a slightly runny consistency. Allow to rest for 10 minutes.
02 - Heat a non-stick skillet over medium heat and lightly brush with melted butter. Pour approximately ¼ cup batter into the skillet, swirling quickly to coat the surface in a thin, even layer. Cook for 1–2 minutes until edges begin to lift and the bottom turns golden brown. Flip and cook for 1 additional minute. Transfer to a plate and repeat with remaining batter.
03 - Heat olive oil in a skillet over medium heat. Sauté the chopped onion until softened and translucent, approximately 3–4 minutes. Add sliced mushrooms and cook until golden brown, about 5 minutes. Stir in chopped spinach and cook just until wilted, 1–2 minutes. Season generously with salt and freshly ground black pepper.
04 - Place approximately 2 tablespoons of the vegetable filling in the center of each crepe, followed by a sprinkle of grated cheese. Fold or roll the crepe securely around the filling. Return filled crepes to the skillet and cook for 1–2 minutes per side to heat through and melt the cheese completely.
05 - Serve immediately while hot, garnished with fresh herbs such as parsley or chives if desired. These crepes pair excellently with a crisp white wine like Sauvignon Blanc or a simple green salad dressed with light vinaigrette.