Preheat oven to 400 degrees. Lightly grease 4 taco molds and place them on a baking sheet. If no molds make some out of foil or lay the chalupas open faced when ready to bake. Place the chicken breasts/thighs onto a parchment or silicone lined work surface. Cover each chicken breast/thigh with another piece of parchment paper.
Use a meat mallet or rolling pin and pound/roll each chicken breast/thigh into a large, thin circle that's about 1/4 inch thick. Each one should be about 6 to 8 inches in diameter. (think the size of a tortilla) In a wide bowl whisk together the egg and mayonnaise until fully combined.
Place the breadcrumbs, parmesan cheese, seasonings and salt into a food processor. Process until very fine (almost powdery) Cover the bottom of a deep plate with some of the breadcrumb mixture. Set the remainder of the crumb mixture aside.
Place the shaped chicken portions one at a time onto another wide plate. Use a basting brush and brush a light layer of the egg mixture over both sides until fully coated. Place one of the coated chicken portions onto the plate with the crumbs. Use a spoon and coat the top and all sides of the chicken. Use the back of the spoon and press the crumbs into the chicken to fully stick.
Place the coated chicken around a taco shell mold or lay flat on a lined baking sheet. (like a tostada shell) If using the molds place the molds on a baking sheet. Spoon more of the crumb mixture over the bottom of the crumb plate and repeat the coating process until all chicken portions are coated and on the molds in the baking sheet.
Place in preheated oven. Bake at 400 degrees for 30 minutes or until lightly crisp and the internal temperature of the chicken is at least 160 degrees.