Flemish hennepin-flavored pancakes with apples

For the pancakes:
2 cups all-purpose flour
1/2 teaspoon salt
1/4 cup sugar
1/2 teaspoon ground cinnamon (optional)
3 large egg yolks
2 1/2 to 3 cups Hennepin Ale
2 tablespoons butter, melted
3 large egg whites, beaten to soft peaks
4 tablespoons of butter, softened at room temperature, for baking
For the apples:
4 firm apples, peeled, cored, and thinly sliced.
3 tablespoons butter
3 tablespoons sugar

1. In a large mixing bowl, sift the flour with the salt, sugar and cinnamon (if used). Make a well in the center. Add the yolks and half of the beer in a steady stream and whisk, gradually drawing in the flour. Add the butter and enough beer to obtain a smooth batter with the consistency of heavy cream. Carefully fold in the egg whites. Cover the bowl and let stand for 30 minutes.
2. In the meantime, prepare the caramelized apples. Heat the butter in a large skillet and fry the apple slices, in batches, over high heat until lightly browned. Turn the apple slices, sprinkle with sugar and caramelize. Reserve.
3. Place an 8- or 9- inch skillet over medium heat and brush with butter. If the batter is too thick, thin with a little more beer. Pour a small ladle of batter into the pan, tilt the pan as to cover its entire surface. Quickly arrange 4 to 5 slices of apple on top (before the batter sets), and bake until lightly browned on the bottom. Turn the pancake with a spatula and brown the other side.
4. Stack the cooked pancakes on a warm plate and serve as soon as possible (or keep warm in a preheated oven). Sprinkle the pancakes with powdered sugar, or serve with Poiret, a typical apple and pear syrup.