In a food processor, pulse together flour, baking powder, salt and baking soda. Add butter and pulse until mixture resembles coarse meal. In a small bowl, mix sour cream and egg. Add to food processor, pulse until almost combined. Add chorizo and cheese and pulse until mixed (dough will look crumbly).
On a lightly floured surface, pat dough into a square about 3/4-inch thick. Using a sharp knife, cut into about 16 triangles and place on a lined baking sheet. Bake until golden, 12 to 14 minutes. Serve with a bowl of sour cream mixed with whole-grain mustard.