Make the dough: Whisk together the sourdough discard and sour cream. Set aside.
56 grams sourdough discard, 75 grams sour cream
Combine the dry ingredients. Rub the butter in until all the flour is coated and pea-sized pieces form.
120 grams all-purpose flour, 5 grams baking powder, 3 grams salt, 113 grams unsalted butter
Make a well in the center of the dough and pour the sour cream mixture in. Stir with a wooden spoon or spatula, then lightly knead the dough to bring it together. It's ok if the mixture is a little bit crumbly.
Turn the dough out on a piece of plastic wrap. Use the edges to bring the dough together. Wrap the dough and flatten into a small, compact rectangle.
Chill the dough: Refrigerate the dough for 15 minutes. This short chill period will allow the flour to hydrate.
Laminate the dough: Unwrap the dough and turn it out on a floured surface. Using a rolling pin dusted with flour, flatten the dough out to a large rectangle (about 14 by 12 inches, it doesn't have to be exact).
Fold the dough in half and then in quarters. Wrap the dough tightly in plastic wrap and refrigerate for 15 minutes. This short rest period will cool down the butter and allow the gluten to relax, making the dough much easier to roll out.
Prep: Preheat the oven to 375 F and line one 18 by 13 inch baking sheet with parchment paper.
Shape: On a floured surface, roll the dough out into a 14 by 10 inch rectangle. Trim the edges of the dough, this will encourage the crust to puff up as it bakes.
Divide the dough into 4 rectangles, cut each one into two equal triangles. Take each triangle and divide it into 3 long triangles. You should end up with 24 triangles.
Place the hot dog on the wide edge of one triangle. Roll the dough out tightly around the hot dog.
6 hot dogs
Transfer each piece on a baking sheet with the point down, this will prevent them from breaking apart while they puff up.
Arrange them with at least 2 inches of space in between to give them room to rise.
Refrigerate the baking sheet uncovered until the oven is hot.
Bake: Whisk the egg. Brush the tops of the dough with egg wash.
1 egg
Bake at 375 F for 15 to 20 minutes or until the dough is golden brown.