Preheat smoker to 225°F with hickory, oak, or pecan pellets. Clean and oil grates.
Form ground beef into 4 patties (8 oz each), ¾-inch thick. Season both sides with salt, pepper, and garlic powder.
Smoke patties at 225°F for 45-60 minutes until internal temperature reaches 135°F (medium-rare) or 145°F (medium).
Meanwhile, fire-roast jalapeños until charred. Remove skin and seeds, then dice. Mix with cream cheese, cheddar, bacon, paprika, and salt.
When burgers are 10°F from target temp, increase heat to high or transfer to hot cast iron. Sear 1-2 minutes per side.
Top each burger with jalapeño popper mixture during final minute of searing. Toast buttered buns until golden.
Assemble burgers with desired toppings and serve immediately.
Notes
Use 80/20 ground beef for optimal juiciness during smoking
Fire-roast jalapeños for authentic popper flavor
Apply topping during final searing for perfect melting
Reverse sear method creates perfect crust and interior