Day 1: 12 hours before baking, mix the sourdough starter, warm water, and honey in a bowl.

Add the flour, mix well, cover, and let it rest for 30 minutes.

Next, add the salt and mix it through. With wet hands, pull and fold the dough from all sides.

Cover it with oiled plastic wrap and let it rise in a warm place for 12 hours (overnight).

In a saucepan, combine the blueberries, sugar, water, lemon zest, and lemon juice; simmer them together.

Make a slurry using cold water and ClearJel, then add it to the blueberry mixture and cook until it thickens.

Allow it to cool, then refrigerate.

Day 2: Preheat your oven to 425°F.

Oil a sheet pan and stretch the dough onto it.

Spread the cooled blueberry filling over the dough and fold the edges over to enclose the filling.

Cover and let it rise for 2 hours until it becomes puffy.

For the crumble topping: Mix together flour, butter, and sugar until combined.

For the lemon glaze: Stir the powdered sugar and lemon juice until smooth.

Dimple the dough with oiled fingers, drizzle it with olive oil and melted butter, add dollops of the blueberry filling, and sprinkle with the crumble topping.

Bake in your preheated oven for 20-25 minutes until it turns golden brown.

Allow it to cool on a wire rack before cutting, and finish with a drizzle of the lemon glaze.