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

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

Transfer dough to a lightly oiled bowl, cover, and refrigerate for at least 12 hours.

Grease a baking pan with melted unsalted butter. Deflate chilled dough and spread it evenly in the pan. Let rise in a warm spot for 1.5 to 2 hours.

Melt unsalted butter in a saucepan until golden brown. Stir in light brown sugar and ground cinnamon.

Preheat oven to 450°F. Use wet fingers to create dimples in the dough. Pour the brown butter mixture over the top.

Bake for 20-25 minutes or until golden brown.

Let cool slightly. Whisk together powdered sugar, milk, and vanilla extract. Drizzle over the warm focaccia before serving.