Combine warm water with granulated sugar in a small bowl. Sprinkle active dry yeast and let sit until foamy.

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

Shape dough into a ball, place in a greased bowl, cover and refrigerate for at least 12 hours for rising.

Preheat oven to 450°F. Grease a baking pan with melted butter. Transfer and press down risen dough into the pan, allow to rise for 1.5 to 2 hours.

Melt unsalted butter in a saucepan until golden brown. Let it cool slightly.

Mix light brown sugar and cinnamon in a bowl, stir into the cooled brown butter.

Dimple the dough, drizzle with the brown butter mixture evenly.

Bake for 20-25 minutes until golden brown. Let cool for 10 minutes before transferring to a rack.

Mix powdered sugar, milk, and vanilla for the icing and drizzle over warm focaccia before serving.