2 large eggs
1 large egg yolk (CI uses 3 whole eggs)
1 cup buttermilk (or milk)
¾ cup rye (or AP, or white wheat) flour
¼ teaspoon kosher salt
2 tablespoons plus 4 tsp. sugar
¼ cup unsalted butter, melted, plus 8 tsp., room temperature
Lemon wedges (for serving)

Blend eggs, egg yolk, buttermilk, and milk in a blender until smooth. Add rye flour, all-purpose flour, salt, and 2 Tbsp. sugar and blend well. With blender on low, gradually stream in melted butter. Strain batter through a fine-mesh sieve into a large measuring cup or medium bowl.

Heat ½ tsp. butter in a medium nonstick skillet over medium heat until foamy. Pour ¼ cup batter into skillet and swirl to coat bottom of pan. Cook crepe until lacy and golden brown on one side, about 2 minutes. Carefully flip crepe and cook on other side until just cooked through, about 1 minute longer; transfer to a plate.

Repeat with remaining batter and stack crepes, placing a piece of parchment paper between each as you go to prevent sticking (you should have 8 crepes).

Just before serving, heat 1 tsp. butter in a large skillet over medium-high heat. Fold 2 crepes in half and place side by side in skillet; sprinkle with 1 tsp. sugar total, then flip. Cook until sugar is beginning to caramelize, about 1 minute. Repeat with remaining crepes.

Serve with lemons for squeezing over.

See further methodology discussion and options (including banana nutella) at Cook's Illustrated and at Bon Appetit