Mushroom Cuban Quesadillas

Name: Mushroom Cuban Quesadillas
Ingredients: 8 large fresh portobello mushrooms (about 1 pound 9 ounces), stemmed and gills removed; 1 tablespoon kosher salt; 2 teaspoons ground cumin; 1 teaspoon garlic powder; 1 teaspoon black pepper; 1 teaspoon grated orange zest; ½ cup plus 2 tablespoons canola oil, divided; ¼ cup whole-grain Dijon mustard, plus more for serving; 4 (9 1/2-inch) flour tortillas; 16 (3/4-ounce) Swiss cheese slices; 1 cup hamburger dill pickle chips, plus more for serving; Sliced scallions, for garnish