In a large mixing bowl, combine 1 cup of sourdough discard, 1 cup of all-purpose flour, 1 tablespoon of baking powder, and 2 tablespoons of olive oil. Stir until a shaggy dough forms.

Cover the shaggy dough with a damp cloth and let it rest for 10 minutes.

Sprinkle flour onto a clean countertop and divide the dough into 12 equal pieces. Roll each piece into a ball and flatten into a 3-inch circle.

Place a mozzarella cube and any additional fillings in the center of each circle. Fold edges up and pinch tightly to seal.

Preheat your oven to 375°F and line a baking tray with parchment paper. Place the bombs seam-side down and bake for 18-20 minutes until golden brown.

Remove from oven and let cool for a few minutes. Serve warm alongside marinara sauce for dipping.