1-First, in a medium bowl, mix the 1 pound ground beef, 1 egg yolk, 1/4 cup shredded Parmesan cheese, 1/4 cup fine sourdough breadcrumbs, 1 and 1/2 teaspoons Cajun or blackening seasoning, and 1 teaspoon Kosher salt if needed. Divide the mixture into three equal portions and gently shape into patties, making a small indent in the center with your thumb to keep them from puffing up.

2-Next, preheat a grill or cast iron skillet to medium heat. Cook the patties for about 4-6 minutes per side until they’re browned and cooked through. Add the 4 slices of sharp cheddar cheese on the burgers about 2 minutes before they’re done, letting it melt just right.

3-While the patties cook, grill the 4 buns, buttered side down, for about a minute to get that crispy edge. For the sauce, mix together the 1/4 cup mayonnaise, 1 tablespoon ketchup, 1 teaspoon molasses or maple syrup, and 1 and 1/2 teaspoons Cajun seasoning in a small bowl. Once everything is ready, assemble the burgers by layering the cheese, 4 leaves of lettuce, sliced 1 red onion, sauce, and patties.