In a large bowl, combine the active, bubbly starter with water, salt, and bread flour. Stir with a dough whisk or spoon until a sticky dough forms. Cover and let it rest for 30 minutes.

Uncover the dough and perform 4-6 coil folds. The dough will be very sticky at this stage but will strengthen with each fold. Wet your hands to prevent sticking. Slide your hands under the center of the dough, lift it up, and let it stretch without tearing. As it releases, fold it under itself. Repeat on both sides, then rotate the bowl and repeat the process. Cover and let it rest for 30 minutes.

Shred the cheeses and toss them with dried herbs in a bowl until evenly mixed. Cover with plastic wrap and set aside.

Wet your hands and note how the dough has strengthened since the last set of folds. Sprinkle half of the cheese mixture over the dough. Cover the remaining cheese and refrigerate. Perform another round of coil folds, gently incorporating the cheese as you fold. Cover and let rest for 30 minutes.

Wet your hands again and perform 3-4 more coil folds, working the cheese into the dough. It’s okay if some pieces aren’t fully incorporated yet. Cover and let rest for 30 minutes.

Repeat the process one last time, then cover and let the dough rest at 78°F for 1.5-2 hours. By now, the dough should have risen about 30-40% with some scattered bubbles on the surface.

In a small bowl, mix olive oil, melted butter, garlic powder, salt, and rosemary.

After the dough has rested, get a 9x13 metal baking pan or a 12-inch skillet ready by coating it with half of the garlic rosemary oil. Tilt the pan to ensure the oil covers the entire bottom. If sticking is a concern, line the pan with parchment paper before adding the oil.

Transfer the dough to the prepared pan and gently stretch it toward the edges. If it resists, let it rest for a minute before trying again. Pour the remaining garlic rosemary oil over the dough, cover with plastic wrap, and proof. If desired, you can refrigerate the dough at this stage for up to 48 hours before proceeding.

Leave the covered dough in a warm spot (78-80°F) for 3-5 hours until it has doubled in size, becomes puffy, and feels very airy. There should be bubbles forming on the surface. If it’s not there yet, give it more time in a slightly warmer space.

Once the dough is well-risen and full of air bubbles, preheat the oven to 425°F. Sprinkle minced garlic evenly over the top, followed by the remaining cheese mixture. Using your fingers, gently press into the dough to create dimples, working from top to bottom until the entire surface is dimpled and bubbly.

Place the pan in the preheated oven and bake for 25-30 minutes, until the focaccia is golden brown, bubbling, and registers 200°F internally. Let it cool in the pan for 5-10 minutes before transferring to a wire rack. Slice, serve, and enjoy!