Whisk together the flours, milk, 3 eggs, melted butter, a few pinches of sea salt and a drizzle of sweetener. Whisk until completely smooth. Let batter rest in the refrigerator for a couple of hours.
Melt the remaining 2 tablespoons butter in a small pot or dish. Heat a crepe pan or a 10-inch skillet over medium-low heat. Brush the pan with some melted butter using a pastry brush and add a scant 1/4 cup or medium ladleful of the crepe batter to the pan. Immediately swirl the pan to coat it evenly with the batter. Cook 1 minute then slide a thin spatula carefully underneath and flip the crepe. Cook a few seconds less on the second side then transfer to a plate. Repeat to make 8-10 crepes.