Tocino Burgers

Cut papaya into 1/8- x 1/8- x 2-inch matchsticks to yield about 6 cups. (Reserve remaining papaya for another use.) Toss together papaya matchsticks and 2 tablespoons salt in a large bowl. Let stand at room temperature 30 minutes.

Transfer papaya mixture to a colander, and rinse under cold water. Using a clean dish towel, squeeze papaya mixture to remove as much excess moisture as possible. Toss together papaya, cabbage, onion, bell pepper, carrot, ginger, and black pepper in a large heatproof bowl. Bring white vinegar, granulated sugar, and remaining 1 teaspoon salt to a boil in a small saucepan over medium-high, stirring often to dissolve sugar. Pour hot vinegar mixture over papaya mixture; toss to combine. Cover and refrigerate until mixture is softened and vibrant in color, at least 30 minutes or up to 3 days.

Stir together mayonnaise, cornichons, banana ketchup, chile vinegar, Korean chile flakes, black pepper, and salt in a medium bowl. Season with additional salt to taste.

Process tocino in a food processor until finely chopped, about 20 seconds. Transfer to a large bowl; add ground pork, brown sugar, sugarcane vinegar, annatto oil, garlic, salt, and black pepper. Using your hands, mix until evenly combined. Divide mixture evenly into 16 balls (about 1 3/4 ounces or 3 tablespoons each). Flatten each ball to a 3-inch-round, 1/2-inch-thick patty. Set patties aside.

Melt 1 tablespoon butter in a large cast-iron skillet over medium. Place 2 ube buns, cut sides down, in skillet, and cook until golden and lightly crisp, about 2 minutes. Remove from skillet. Repeat process 3 times with remaining 3 tablespoons butter and remaining 6 buns. Set toasted buns aside. Increase heat under skillet to medium-high. Working in batches, cook pineapple slices in skillet until browned and starting to char on both sides, about 4 minutes per batch. Transfer pineapple to a plate. Do not wipe skillet clean.

Add canola oil to skillet, and reduce heat to medium. Arrange 4 tocino burger patties in skillet, and press firmly with a spatula to flatten to about 1/4-inch thickness. Cook until browned on both sides and a thermometer inserted in thickest portion of meat registers 160°F, about 2 minutes per side. Transfer to a rimmed baking sheet, and tent with aluminum foil to keep warm. Repeat process with remaining 12 tocino burger patties (no need to add more oil in between batches).

Spread about 1 tablespoon secret sauce on each top ube bun half. Top each bottom bun half with 1 pineapple slice, 2 tocino burger patties, about 1/3 cup green papaya achara, and top bun half. Reserve remaining green papaya achara for another use. Serve burgers with additional secret sauce, if desired.