In a mixing bowl, whisk together milk and eggs until fully combined and frothy. Gradually add all-purpose flour, mixing gently until a smooth batter forms. Let the batter rest for 15 minutes.

Heat a non-stick skillet over medium heat and lightly grease it with unsalted butter. Pour in a ladleful of the batter, swirling the skillet to evenly cover the bottom. Cook for about 2 minutes until the edges turn golden, then flip and cook for another 1-2 minutes.

In the same skillet, add olive oil and sauté spinach over medium heat until wilted. In a bowl, scramble eggs with salt and pepper; pour into the skillet. Stir until fluffy, then mix in cheddar cheese until melted.

Lay one crepe flat on a plate. Spoon a portion of the spinach and cheese filling in the center, then gently fold the crepe over. Repeat for remaining crepes and serve warm.