Mix together 5 grams ripe sourdough starter with 55 grams water and 55 grams flour. Cover and let sit overnight at 78ºF until doubled in size, bubbly and active. You can also substitute 100 grams of bubbly sourdough starter if you prefer.

Mix: Mix together ripe, bubbly, active levain with water, freshly grated apple, granulated sugar, salt and bread flour. Mix together with a dough whisk or spoon until a sticky dough forms. Cover and let rest for 30 minutes.

Coil Fold # 1: 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. Watch a video of the coil fold process here. Cover and let rest for 30 minutes.

Coil Fold #2: 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.

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

Coil Fold #4: Repeat the last set of coil folds.

Finish Bulk Fermentation: Cover and rest the dough at 78ºF for 2.5-3 hours until the dough has risen about 50-60% in the bowl.

Prepare Filling: Mix together brown sugar and cinnamon until combined.

Prepare the Pan: After the long bulk rest, line a 12 inch round or 9 by 13 metal baking pan with parchment paper. Pour 50 grams light-flavored olive oil in the pan. Tip the pan around to coat the entire bottom of the parchment paper.

Shape the Dough: Dump the focaccia dough into the pan and spread out with your fingers. Pour half of the cinnamon sugar mixture on top of the focaccia dough. Fold the dough in half and sprinkle the rest of the mixture on the dough. Fold again. At this point the dough will be all together in the middle of the pan. Don't worry about spreading it out yet. At this point you can cover the dough and refrigerate it for up to 48 hours before proceeding with a second proof and baking.

Proof the Dough: Let the dough sit in a warm 78-80ºF place for 2-3 hours until doubled in size, puffed up and very airy. If the dough doesn't look like this, warm it up a little more and let it rise longer.

Prepare the Crumb Topping: Add softened butter, brown sugar, cinnamon, flour and and salt to a small bowl. Use your fingers or a spoon to stir together until a thick crumb topping is formed. Set aside.

Dimple the Dough: 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. Sprinkle the crumb topping all over the top of the risen 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.Optional: For more apple flavor, add some freshly grated apple to the top of the focaccia along with the crumb topping.

Bake Focaccia: 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.

Sweet Glaze: While the focaccia is baking, mix together the glaze. Whisk powdered sugar, milk, vanilla extract and salt together. Pour over the warm focaccia. Enjoy!