Combine flour and salt in a large bowl.
Cut in butter until mixture is dry and crumbly.
Stir in beaten egg, cheese, and jalapeño.
Roll into a ball, cover with plastic wrap, and refrigerate for 1 hour.
Preheat oven to 400°F (200°C).
Shape dough into 1-inch balls and place on a greased or lined baking sheet, a few inches apart.
Flatten each ball with a mug or jar.
Bake for 15 minutes or so, or until lightly golden.
Cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely before serving.