In a medium bowl add ground chuck, and sprinkle the following evenly over the meat; kosher salt, black pepper, garlic powder, and if using bouillon. Mix quickly, careful not to overwork the meat. Divide meat into 8 similar-sized meatballs.
Return the burger balls to the refrigerator or freezer until ready to grill, no longer than 20 minutes in the freezer.
Prepare Smash Sauce (optional)
Mix all the sauce ingredients in a small bowl, and place in the fridge until ready to use.
Grill Onions
If making caramelized onions, on the flat top grill, over medium heat, melt butter and add sliced onions, sprinkling with salt. Grill, tossing occasionally until caramelized, about 15 minutes. Scoot to the back and side, where they can continue cooking, stirring occasionally.
Grill Buns
Butter buns and grill until golden brown, set aside. Have toppings sliced and ready to build your smashburger.
Grill Smash Burgers
Increase grill temperature to the higher side of medium-high heat. Once hot, place 4 burger balls onto the griddle, to keep the meat from sticking, place a square of parchment paper onto the top of the meatball, then immediately smash straight down on the burgers, so they become a thin patty.
Use a wide steel spatula, you may have to use your hand or something else to push down on the spatula or a burger press (you may also use the bottom of a large glass or jar).
Grill for 2 minutes, flip, add cheese if desired, and cook for 1-2 minutes. Add cheese during last minute or two until melted.
Build your burger, by adding smash sauce to the bottom bun, adding shredded lettuce, a slice of tomato, and pickles, then add burger(s) and top with caramelized onions topping with the top bun.
Notes
Smash Sauce
½ cup mayonnaise, good quality, I like Avocado mayo
1 tablespoon sweet pickle relish
1 tablespoon Dijon mustard
1 teaspoon fresh lemon juice
½ teaspoon seasoning salt (like Lawry’s)
Mix all ingredients together, keep in fridge until ready to use. Store leftovers in airtight container. StorageStore any leftover smash patties in an airtight container in the refrigerator, lasting 4 to 5 days. You can also freeze your burgers in a freezer safe container. Or, freeze your pre-portioned burger balls, defrost them, and smash them on the griddle when you're ready.