Activate the yeast: In a small bowl, combine the warm water and granulated sugar. Sprinkle the active dry yeast over the top and let it sit for 10-15 minutes until it becomes foamy.

Mix the dough: In a large mixing bowl, whisk together the flour and salt. Pour in the activated yeast mixture along with the olive oil. Stir until a sticky dough ball forms.

First rise: Cover the bowl with a damp tea towel or plastic wrap and place it in the refrigerator for at least 12 hours.

Second rise: Grease a baking pan and line it with parchment paper. Pour melted butter into the center. Place the risen dough into the pan. Cover it and let rise for another 1.5 to 2 hours.

Make the brown butter: Melt butter over medium heat, stirring until golden-amber. Cool for about 10 minutes.

Make the cinnamon topping: Mix brown sugar and cinnamon into the browned butter until dissolved.

Dimple the dough: Preheat the oven to 450°F. Wet fingers and press dimples into the dough. Drizzle the cinnamon-butter mixture over the dough.

Bake: Place in the oven and bake for 20-25 minutes or until golden brown. Let cool for 10 minutes, then transfer to a rack.

Finish with icing: Combine powdered sugar, milk, and vanilla extract. Drizzle over warm focaccia and slice into squares.