Preheat oven to 450°F. Coat a baking sheet with cooking spray.
Heat 1½ teaspoons oil in a large nonstick skillet over medium-high heat. Add onion and celery; cook, stirring, until softened, about 3 minutes. Stir in parsley; remove from the heat.
Place salmon in a medium bowl. Flake apart with a fork; remove any bones and skin. Add egg substitute and mustard; mix well. Add onion mixture, breadcrumbs and pepper; mix well.
Shape the mixture into 8 patties, about 2½ inches wide.
You can fire up the grill and grill these patties or cook over the stove as below.
Heat remaining 1½ teaspoons oil in the skillet over medium heat. Add 4 patties and cook until the undersides are golden, 2 to 3 minutes. Using a wide spatula, turn them over onto the prepared baking sheet. Repeat with the remaining patties.
Bake the salmon cakes until golden on top and heat for 15 to 20 minutes.
Meanwhile, prepare Cilantro Serrano Sauce. Serve the salmon cakes over a bed of mixed greens with sauce and lemon wedges.