Add all purpose flour, sugar and salt to a food processor and pulse to combine
Add the cubed, chilled butter and pulse until crumbs are the size of peas
Add chilled sourdough starter and pulse until dough starts to form
Remove onto a lightly floured surface. Divide into two pieces
Gently shape each piece into a ball, careful not to add too much flour
Wrap each ball individually in plastic wrap and chill for 1 hour before using