Add the milk, water, eggs, and melted butter to a high-speed blender. Blend for 15 seconds, or until completely combined.
Add the flour (and any optional flavorings) and pulse for an additional 10 seconds, or until any large dry clumps are gone. Scrape down the sides of the blender as needed.
Place the crêpe batter in the fridge to chill for at least 30 minutes– or up to overnight. Chilling the batter helps absorb extra water, so the crêpes are thin and crisp– don’t skip this step!
Heat a large (8”) nonstick skillet over medium-low heat. When the pan is just warm, add about ½ teaspoon of butter to the skillet. You want just enough butter to melt and coat the skillet evenly.
When the butter has melted, pour ¼ cup of batter into the center of the pan. As you pour the batter, tilt the pan into a circle– this will help the batter spread into an even circle. If you can’t get the hang of tilting the pan, don’t worry! Just pour the batter into a circle and shake the pan gently to spread the batter into a thin layer– they won’t be as perfectly round, but the crêpes will still be delicious.
Cook for 1–2 minutes, or until the crêpe is golden brown around the edges and on the bottom side. Then flip the crêpe and cook for an additional 1–2 minutes.
Repeat steps 3-5 with the remaining crêpe batter, adding more butter to your pan as needed.
Serve with your favorite fillings.