1/2cupfine seasoned bread crumbssee above for gluten free options
Barbecue sauce for basting and toppings as desired
In a medium pan, melt butter over medium heat and add onions, stirring until coated. Cook over medium heat, stirring occasionally, for 5-8 minutes, until tender and translucent.
Add brown sugar and continue cooking for another 8-10 minutes, until caramelized.
Add garlic, chili powder, salt and pepper and cook over medium heat 1 minute. Remove from heat, scrape into a bowl and refrigerate until room temperature (if you're making this ahead, be sure to cover the dish after the onions have cooled to store for longer periods of time).
In a large bowl, combine pork, beef, egg, bread crumbs, vinegar worcestershire sauce and cooled onion mixture and mix just until combined -- don't overmix.
Shape into 8 patties for ¼ pound burgers (feel free to make them bigger or smaller according to your preferences).
*Recommended: place on a baking sheet, cover with plastic wrap and refrigerate for at least 2 hours or up to 24 hours. You can also place in the freezer for 2-3 hours. This isn't necessary but really helps the flavors meld together and helps the burgers stay together when cooked.
In a pan or on a grill, cook burgers for about 4-5 minutes per side on medium-high heat until internal temperature reaches 160 degrees F. Serve as desired with buns, garnishes, sauces, etc.