Mix together 6 grams ripe sourdough starter with 60 grams water and 60 grams flour. Cover and let sit overnight at 78ºF until doubled in size, bubbly and active.

Mix together ripe, bubbly, active levain with water, granulated sugar, salt, and bread flour. Mix together with a dough whisk or spoon until a sticky dough forms. Cover with plastic wrap or a bowl cover and let rest for 30 minutes.

Take the cover off the dough and perform 4-6 coil folds. The dough will be very sticky for this first set of coil folds but will strengthen over time. Wet your hands with water. Place your hands under the middle of the dough and pull up. The dough will stretch up (but should not tear) and release from the bottom of the bowl. Once the dough releases, let the dough fall back under itself. Repeat the process for both sides of dough. Then turn the container and repeat the coil fold. Cover and let rest for 30 minutes.

Wet your hands. You will notice the dough is stronger than your first set of folds. Repeat the coil folds, noticing how the dough is changing and strengthening over time. Cover and rest for 30 minutes.

Wet your hands. Perform 3-4 coil folds. Cover and rest for 30 minutes.

Repeat the last set of coil folds, noticing how strong and developed the dough feels at this point.

To a small saucepan add the blueberries, raspberries, blackberries, sugar, cornstarch, lemon juice and a pinch of salt. Set over medium heat and mash the berries, breaking them down and releasing their juices. Once the berries are mashed, continue whisking and cooking over medium heat until thickened and coating the back of a spoon, about 5 minutes. Pour the berry filling into a bowl and set aside to cool to room temperature.

Cover and rest the dough at 78ºF for 2.5-3 hours until the dough has risen about 50-60% in the bowl, has scattered bubbles around the edges, and is very jiggly.

After the long bulk rest, line a 12-inch round or 9 by 13-inch metal baking pan with parchment paper. If your pan is non-stick, you can skip the parchment. Pour 40 grams of light-flavored olive oil into the pan. Tip the pan around to coat the entire bottom of the parchment paper.

Transfer the focaccia dough to the pan and gently spread it out with your fingers. Spoon about ⅓ of the filling over the surface. Fold one side of the dough toward the center and spread another ⅓ of the filling on top. Fold the opposite side over, then spread the remaining filling on top. Gently roll or fold the dough into a square shape in the center of the pan. Don’t worry about pressing it out yet—just let it rest in the center.

Cover the dough and let it sit in a warm 78-80ºF place for 2-3 hours until doubled in size, puffed up and very airy.

After the dough is puffed up, jiggly, and aerated with air bubbles, gently spread the dough out to fill the edges of the pan. Pour 30 grams of melted butter on top of the dough. Take your fingers and gently dimple the dough. Start at the top and work your way down the dough until the entire focaccia is dimpled and bubbly. Add blueberries, raspberries and blackberries to the top of the dough.

Pre-heat the oven to 425ºF. Once the oven is pre-heated, bake the focaccia for 25-30 minutes until bubbly, crispy and light golden brown on top and the baked focaccia registers 200ºF. Let cool in the pan for 5-10 minutes before removing to a wire rack.

While the focaccia is baking, mix together the vanilla glaze. Whisk powdered sugar, milk, vanilla extract and salt together. Drizzle over the warm focaccia.