
Place the flour in a large bowl and, using a pastry cutter, cut in the cold butter until the mixture is crumbly. Mix the egg into the sour cream and add to the flour mixture. Stir with a fork until just combined. Form the dough into three balls, wrap well in plastic wrap and refrigerate at least 3 hours or overnight. (See Note.)
There are different ways to roll out the dough balls. Mom's recipe calls for rolling out each of the three dough balls, then cutting them into 16 triangles and sprinkling with the filling. I cut each of the balls into four, then rolled those out and cut each into four triangles. (Next time, I'll try Mom's method.)
Either way, roll the dough out into a round on a lightly floured board with a sprinkling of flour on the dough and the rolling pin. Cut into the desired number of triangles and then sprinkle evenly with the filling. Roll up from the wide end and place on the baking sheets, seam side down. If you like, you can bend the butter horns slightly into a crescent shape or just leave them straight.
Note that this simple dough needs to rest at least 3 – 4 hours. You can leave it in the fridge overnight or even up to a few days too. It can also be frozen for later use (within 2 – 3 months).
Butter Horns https://urbancottagelife.com/butter-horns/