Place chips in a food processor and pulse until coarsely ground. Add beans and pulse until ground. Transfer to a large bowl. In a separate bowl, whisk together eggs, garlic, chili powder, cumin, and salt.
Combine egg and bean mixtures; stir well. Add pepper and scallions, and mix until well combined. Form into 6 patties.
Coat both sides of burgers and tortillas, as well as the grill rack (or nonstick skillet), with cooking spray. Cook burgers over medium, turning, until golden brown and cooked through, 3 minutes per side. Top with cheese (if using) and let melt. Grill tortillas for about 2 minutes. Serve on tortilla rounds topped with salsa.