Preparation
Step 1
Make the batter: Beat eggs in a medium bowl, then whisk in milk, flour, butter and salt. Strain through a fine-mesh sieve into another bowl. The consistency should be that of heavy cream; thin with milk as necessary. Let rest 30 minutes before using or cover and refrigerate overnight. (If the batter isn’t thin enough, crepes will be too thick and won’t spread properly in the pan.)
Step 2
Make the filling: Put ricotta in a bowl. Stir in zest, sugar and salt with a wooden spoon and mix well until smooth and spreadable.
Step 3
Make the crepes: Set an 8-inch nonstick skillet over medium heat. (Alternatively, use a steel crepe pan or cast-iron skillet.) With a paper towel, rub the pan with softened butter. When hot, pour in ¼ cup batter, then lift the pan and quickly swirl with one hand to distribute a thin layer all the way to the edges. Leave pan on the heat for 30 seconds or so, until the crepe starts releasing at the edges. With a spatula (or quickly grabbing edge with fingertips), flip crepe and cook for 15 seconds. Remove crepe to a plate and repeat until all batter is used, stacking crêpes on the plate as you go.
Step 4
With the browned side down, spread the bottom of each crepe with about 2 tablespoons ricotta filling. Fold crepe over to make a half-moon, then fold once more to form a triangle, and place on a buttered baking sheet. Repeat with remaining crepes. Set aside at cool room temperature or refrigerate until ready to serve.
Step 5
Make the sauce: In a small saucepan, place butter, sugar, zest, orange juice over medium-high heat. Bring to a brisk simmer and cook, stirring, for 5 to 10 minutes, until slightly thickened. Turn off heat and stir in liqueur.
Step 6
To serve, heat oven to 350 degrees, and warm the crepes for a few minutes until warm. Put 1 or 2 warm crepes on dessert plates. Spoon about 3 tablespoons sauce over each. Serve hot.