Preheat the oven to 400℉. Line a baking sheet with parchment paper.

Whisk the flour, sugar, baking powder, and salt together in a large bowl. Cut the cold cubed butter into the flour mixture using a pastry cutter until the pieces of butter are the size of peas. Fold in the chopped jalapeños and shredded cheese.

In another bowl, whisk together the buttermilk and egg. Add to the flour/butter mixture and gently fold with a spatula until the dough just starts to come together. Turn the contents of the bowl onto the countertop and knead/press the mixture just until the dough comes together.

Shape the dough into 3 even rounds each about 1 inch thick. Cut each round into 4 even wedges using a pizza cutter or large knife and arrange them on the prepared baking sheet. Bake in the preheated oven for 17-20 minutes or until lightly golden. Let cool on the baking sheet for 10 minutes before serving. Enjoy!