Grilled Pizza Panini Sandwich Recipe

Name: Grilled Pizza Panini Sandwich Recipe
Ingredients: For the Sundried Tomato Pesto; 1/2 cup oil-packed sundried tomatoes; 1/4 cup packed fresh basil; 2 tablespoons pine nuts, toasted; 1 1/2 tablespoons grated Parmesan; 1 medium clove garlic; About 1/2 cup extra-virgin olive oil; 10 ounces cremini or baby bella mushrooms, sliced; 1 medium yellow onion, halved, sliced; 1 pound pizza dough; All-purpose flour, for rolling; 1 teaspoon extra-virgin olive oil, plus more for brushing pizza; Kosher salt; 8 ounces mozzarella cheese, sliced or shredded; 1/2 teaspoon red pepper flakes