Step 1: Prepare the Bacon-Jalapeño Popper Filling. In a medium bowl, combine the crumbled crisp bacon, finely diced jalapeños, softened cream cheese, shredded cheddar cheese, 1/4 tsp garlic powder, and a pinch of salt and black pepper. Mix thoroughly until well combined. Divide the mixture into 4 equal portions and flatten each into a thin disc, about 2 inches in diameter. Place these discs on a small plate or baking sheet lined with parchment paper and freeze for at least 15 minutes to firm up.
Step 2: Make the Ranch Burst. In a small bowl, whisk together the mayonnaise, buttermilk, chopped fresh chives, chopped fresh dill, 1/2 tsp garlic powder, 1/4 tsp onion powder, and a pinch of salt and black pepper. Stir until smooth. Taste and adjust seasoning as needed. Set aside.
Step 3: Prepare the Burger Patties. Divide the ground beef into 8 equal, loosely formed balls. Do not overwork the meat. Season each ball generously with salt and freshly ground black pepper.
Step 4: Toast the Buns. Lightly butter or brush the cut sides of the brioche buns with oil. Heat a large cast-iron skillet or griddle over medium heat. Toast the buns, cut-side down, for 1-2 minutes until golden brown. Remove and set aside.
Step 5: Cook the Smash Burgers. Increase the heat of the skillet or griddle to high until it's smoking lightly. Place 4 of the seasoned beef balls onto the hot surface. Immediately place one frozen jalapeño popper disc on top of each beef ball. Then, place the remaining 4 seasoned beef balls on top of the popper discs, creating a 'sandwich' around the filling.
Step 6: Smash and Sear. Using a sturdy metal spatula or a dedicated burger press, firmly and quickly smash each stacked patty down to about 1/4-inch thick. Cook for 2-3 minutes until a deep brown, crispy crust forms on the bottom. Carefully scrape under the patties and flip them over.
Step 7: Finish Cooking. Cook for another 2-3 minutes on the second side until cooked through and the cheese filling is hot and gooey. If desired, you can add an extra slice of cheddar or pepper jack cheese on top during the last minute to melt.
Step 8: Assemble and Serve. Spread a generous amount of the prepared Ranch Burst dressing on both halves of each toasted bun. Layer with a lettuce leaf, a tomato slice, and the hot bacon-stuffed jalapeño popper smash burger patty. Top with the other bun half and serve immediately. Enjoy your epic burger!