01 - In a large mixing bowl, combine the flour, instant yeast, and fine sea salt. Pour in the warm water and 3½ tablespoons of olive oil. Stir with a wooden spoon until a sticky, shaggy dough comes together.
02 - Knead the dough gently directly in the bowl for 1 to 2 minutes until it becomes slightly smoother. Cover tightly with plastic wrap or a damp kitchen towel. Place in a warm, draft-free spot and let rise for 1 to 2 hours, or until doubled in volume.
03 - While the dough rises, heat 1 tablespoon of olive oil in a small saucepan over medium heat. Sauté the minced garlic until fragrant, about 30 seconds. Stir in the passata, dried oregano, salt, and sugar. Reduce the heat and simmer gently for 10 minutes until slightly thickened. Remove from heat and let cool.
04 - Coat a large baking sheet (approximately 12x16 inches) generously with olive oil. Turn the risen dough out onto the prepared sheet. Using oiled fingertips, gently press and stretch the dough toward the edges. If the dough springs back, let it rest for 15 minutes before continuing to stretch.
05 - Preheat the oven to 425°F, positioning the rack in the center.
06 - Press deep dimples across the surface of the dough using your fingertips. Drizzle lightly with additional olive oil. Bake for 10 minutes until the crust is just set but not yet browned.
07 - Remove the par-baked focaccia from the oven. Spread the cooled pizza sauce evenly over the surface. Scatter the shredded mozzarella in an even layer, then arrange the pepperoni if using, sliced bell peppers, red onion, black olives, and mushrooms. Finish with a generous crack of black pepper.
08 - Return the assembled focaccia pizza to the oven and bake for an additional 15 minutes, or until the cheese is fully melted, bubbling, and the edges of the crust are deeply golden.
09 - Allow the focaccia pizza to rest for 5 minutes after removing from the oven. Sprinkle with chopped fresh basil, slice into squares, and serve warm.