To make spicy caramelized Mayo, heat oil in a large skillet over medium-high heat. Cook onion in hot oil for 7 minutes or until browned (caramelized), stirring occasionally. Reduce heat to medium. Add shallot and curry paste; cook and stir for 2 minutes more. Transfer mixture to a mixing bowl; cover and chill. Stir mayonnaise or salad dressing into chilled onion mixture. Cover and refrigerate for 1 hour or until ready to serve.

Combine ground beef, shrimp, dill, sea salt, and pepper in a large bowl; mix well. Shape mixture into 4 patties about 1 inch thick.

Place burger patties on the lightly oiled rack of the grill directly over medium heat. Grill for 18 to 23 minutes or until an instant-read thermometer inserted in centers register 160 degree F, turning burgers once halfway through grilling.

Toast rolls on grill, if desired; serve burgers on rolls. Top with some of the Spicy Caramelized Mayo, and, if desired, lettuce, sliced tomatoes, and sweet pickle slices. Makes 4 burgers.

Make the Spicy Caramelized Mayo up to 3 days ahead of time. Cover and refrigerate until ready to use.

The internal color of a burger is not a reliable doneness indicator. A beef patty cooked to 160 degrees F is safe, regardless of color. To measure the doneness of a patty, insert an instant-read thermometer through the side of the patty to a depth of 2 to 3 inches.