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.

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

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.

Repeat the coil folds, noticing how the dough is changing and strengthening over time. Cover and rest for 30 minutes.

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

Mix together brown sugar and cinnamon until combined.

Line a baking pan with parchment paper. Pour 40 grams of light-flavored olive oil in the pan.

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.

Let the dough sit in a warm place for 2-3 hours until doubled in size.

Prepare the Crumb Topping: Add softened butter, brown sugar, cinnamon, flour and salt to a small bowl. Stir together until a thick crumb topping is formed.

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.

Pre-heat the oven to 425ºF. Bake the focaccia for 25-30 minutes until bubbly, crispy and light golden brown.

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