In a small bowl, combine warm water with white sugar and sprinkle yeast over top. Let sit for 10-15 minutes until foamy.

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

Cover and refrigerate for at least 12 hours.

Grease a baking pan and transfer the dough, spreading it evenly. Let rise for 1.5 to 2 hours.

Prepare brown butter by melting unsalted butter until golden-amber and nutty. Cool slightly.

Mix light brown sugar and cinnamon in a bowl. Stir into cooled brown butter until dissolved.

Preheat oven to 450°F (232°C). Dimple risen dough with fingers, pour topping over evenly.

Bake for 20-25 minutes until golden brown. Let cool in the pan for 10 minutes.

Make glaze by mixing powdered sugar, milk, and vanilla until smooth. Drizzle over cooled focaccia.