Spinach Artichoke Dip

Name: Spinach Artichoke Dip
Ingredients: 8 tablespoons (1 stick) butter, plus more for buttering the casserole dish; 1/4 cup minced garlic; One 10-ounce bag fresh baby spinach; Kosher salt and freshly ground black pepper; Two 14-ounce cans artichoke hearts, rinsed, drained and quartered; 3 tablespoons all-purpose flour; 1 1/2 cups whole milk, plus more if needed; One 8-ounce package cream cheese, softened; 3/4 cup grated pepper Jack cheese, plus more for topping; 1/2 cup crumbled feta; 1/2 cup grated Parmesan; 1/4 teaspoon cayenne; Salted Pita Wedges, recipe follows, for serving; 6 pita breads; 1/2 cup olive oil; 1 tablespoon kosher salt