In a small bowl, mix warm water with granulated sugar. Sprinkle active dry yeast on top and let it sit for 10-15 minutes until foamy.

In a large mixing bowl, whisk together bread flour and salt. Add the foamy yeast mixture and olive oil, stirring until a sticky dough forms.

Lightly coat the dough with olive oil, seal the bowl and refrigerate for at least 12 hours.

After resting, let the dough sit at room temperature for about 30 minutes. Grease a baking pan and pour in melted unsalted butter, then transfer the dough.

Melt unsalted butter in a saucepan over medium heat until golden brown. Stir in brown sugar and ground cinnamon until combined.

Preheat the oven to 450°F. Create dimples in the risen dough and drizzle the brown butter cinnamon mixture over.

Bake for 20-25 minutes until golden brown and edges are crisp.

Prepare the glaze by whisking powdered sugar, milk, and vanilla extract until smooth. Drizzle over warm focaccia.