In a large skillet over medium heat, warm the oil. Add the garlic, artichokes, spinach, and salt and stir to combine. Let cook for 6-8 minutes, or until spinach is thawed and water has evaporated, stirring occasionally.
Turn off the heat and stir in the cream cheese until combined. If adding chicken, stir it in here.
Lay your tortillas out. Sprinkle about ½ cup mozzarella on half of the tortilla, followed by ¼ of the spinach/artichoke mixture, and then another ½ cup of mozzarella. Fold into a half moon shape.
Clean/wipe out the skillet. Set it over medium heat and drizzle a bit of olive oil in the pan, using a brush to spread the oil to coat the pan (or you can brush oil on the tortillas). Carefully place the tortillas in the skillet and cook for 3-5 minutes or until golden and crispy. Carefully flip and repeat on the other side. Repeat with remaining tortillas.
Slice up your quesadillas. Warm up your marinara sauce to serve on the side for dipping.