Preheat your oven to 425 degrees Fahrenheit and line a baking sheet with parchment paper.
Place the milk in a jar and add the lemon juice. Stir well and leave to sit for 5 minutes.
Place the flour, cornmeal, baking powder, baking soda, sugar, and salt in a food processor and blend.
Add the butter chunks and pulse 10 times to make it appear like breadcrumbs.
Transfer the dough to a bowl and add in your soured milk. Mix until a soft dough has been created.
Knead on a lightly floured worktop to bring the dough together. Cut out circles approximately 1 inch thick and 2 inches in diameter.
Transfer to the baking sheet and bake for 12-15 minutes or until golden brown.