Decide whether you're using 1 or 2 jalapeño, peppers (1 for mild spice, 2 for medium-high spice). Wearing disposable kitchen gloves, slice the jalapeños in half, and remove all the seeds and pith. Dice the jalapeños really finely, as fine as you can dice them.
In a small or medium bowl, combine the cream cheese with half of the diced jalapeños, ¼ teaspoon garlic powder, and ¼ teaspoon onion powder. Use a fork to mix well.
In a large bowl, combine 1 lb ground beef with half of the diced jalapeños, 1 teaspoon salt, ½ teaspoon each garlic powder and onion powder, and ground black pepper. Use your hands to mix it the seasonings and jalapeños into the ground beef, but do not overwork the mixture.
Divide the ground beef mixture into 6 parts (split it in half, then divide each half into 3 equal parts). Form 3 large thin patties (as thin as you can get them, try to make them a little larger than your buns) and place them on a large plate or cutting board. Spoon about 1.5-2 tablespoons of the cream cheese mixture onto each patty and spread it out evenly, making sure to leave at least ½ inch around the edges. Form 3 more patties and place them on top. Use your fingers to gently pinch and seal the edges of the patties so the cream cheese is completely sealed in.
Preheat a medium-large skillet. Once the skillet is hot, add the olive oil. Carefully place the burgers in the pan, cover with a lid, and cook for 3-4 minutes per side over medium heat, or until they're cooked to your liking.
Place a slice of cheese on top of the burger patties and let the cheese melt.
Put together your burger: place lettuce, tomato, and a burger patty with cheese on a bun. Add ketchup, any other burger toppings you like, and serve immediately.
Notes
→ Other add-in ideas: You can use your favorite burger seasonings or add-ins. Try dried oregano, diced fresh chives or scallions.→ Not into cream cheese? Skip the cream cheese filling. Season the ground beef with diced jalapeños and ½ teaspoon each garlic and onion powder.→ Make sure to seal the burger patties really really well on the edges. It's OK if some of the cream cheese comes out on the side as the burgers shrink in size due to cooking, but you don't want the burgers to open up completely.→ Scaling up the recipe: This recipe makes 3 juice third-pounder burgers. If you want to make 4 patties, increase the ground beef to 1.5 lbs, and increase the salt to 1.5 teaspoons, the garlic and onion powder to ¾ teaspoons each. → Nutrition facts: The nutrition facts are estimated for the burger patties only, assuming 93% lean ground beef, and will vary depending on the actual ingredients used.