In a small bowl, mix warm water with sugar and sprinkle the active dry yeast. Let sit for 10-15 minutes until frothy.

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

Cover the bowl and refrigerate for at least 12 hours.

Allow dough to sit at room temperature for 30 minutes, then grease a baking pan and transfer the dough.

Melt unsalted butter in a saucepan until golden brown, then let cool.

Combine the brown butter, light brown sugar, and cinnamon, then mix until smooth.

Preheat the oven to 450°F. Dimple the dough, pour over the brown butter mixture.

Bake for 20-25 minutes until golden brown.

Mix powdered sugar, milk, and vanilla for icing. Drizzle over warm focaccia.