Preheat and prep. Set your oven to 425°F (220°C). Line a sheet pan with foil or parchment for easy cleanup.
Toast the bread base. Slice the French bread lengthwise. Brush cut sides with olive oil and sprinkle with garlic powder, a pinch of salt, and pepper.
Place cut-side up and bake for 5–7 minutes until lightly crisp. This prevents sogginess.
Season the chicken. In a bowl, toss the chicken with 1/2 cup BBQ sauce. Add more if you like it extra saucy, but don’t drench it; you’ll add more sauce to the bread.
Sauce the bread. Spread a thin layer of BBQ sauce over the toasted bread halves. Thin and even is key for crisp bottoms.
Add cheese and toppings. Sprinkle on half the mozzarella and cheddar.
Distribute the BBQ chicken evenly. Scatter the red onions and jalapeños (if using). Top with the remaining cheese.
Bake. Return to the oven for 8–12 minutes, until the cheese is melted and edges are golden.
Broil for finish. Switch to broil on high for 1–2 minutes to brown the cheese slightly.
Watch closely to avoid burning.
Garnish and rest. Let the pizzas sit for 3–5 minutes to set. Drizzle with a little more BBQ sauce if you like and sprinkle with fresh cilantro or parsley.
Slice and serve. Cut into pieces with a sharp knife or pizza wheel. Serve hot with a crisp salad or roasted veggies.