If you are using yeast, follow the instructions here up to step 4 (right after the dough is done rising). If you are using sourdough, follow the instructions here, up to step 1 (right after the dough is done rising). 2. Pour 3 tablespoons of the melted, unsalted butter into a 9×13 inch baking dish. Use your hands or a brush to evenly coat the bottom and sides. Gently remove the dough from the bowl and place in pan. Drizzle 3 more tablespoons unsalted butter on top of the dough.

In a small bowl, stir together the brown sugar and cinnamon. Sprinkle ½ of the mixture over the focaccia dough. If you are adding a topping (such as chopped apples, pecans, blueberries, or lemon zest), sprinkle ¾ of the topping over top of the brown sugar cinnamon. Fold the dough, starting at the top, ⅓ of the way down. Grab the dough at the bottom, and fold the bottom, ⅓ of the way up and over top of the portion that you just folded, as if you were folding a letter. Gently press/stretch the dough out to mostly fit the 9×13 inch pan. Drizzle the remaining 2 tablespoons butter over top of the dough. Sprinkle the remaining half of the brown sugar cinnamon mixture over top of the dough. Add the remaining topping (apples, pecans, blueberries or lemon zest), if using, over top.

Cover pan with plastic wrap and allow dough to rise 2 hours at room temperature OR, turn oven on until the temperature reaches 100F. Once oven reaches this temperature, turn oven OFF. Place covered dough in warm oven and allow to rise for 1 hour. Remove from the oven.

Preheat oven to 425F.

Using the tips of your fingers, press into the dough to make indents in the dough.

Bake in preheated oven for 25-30 minutes, or until golden brown in color.

Meanwhile, make the icing. Beat together the butter, sugar and vanilla extract until smooth and creamy. Spread/drizzle over the warm focaccia. Slice and enjoy!