Old-school Swedish meatballs get a Korean twist, courtesy of gochujang, a spicy, subtly sweet fermented chili paste.
In a large bowl, use your hands to gently combine garlic, ginger, 3 tablespoons gochujang, beef, pork, egg, and 1 tablespoon salt just until evenly combined (do not overwork, or meatballs will be dense and tough). Scoop 1 tablespoon of mixture into your palm; gently roll into a ball and transfer to a baking sheet. Repeat with remaining mixture. Meatballs can be formed, loosely covered, and refrigerated on sheet up to 1 day.
Heat a large skillet over medium-high. Swirl in 2 tablespoons safflower oil. Add halfof meatballs in a single layer and cook, turning a few times, until browned in places and a crust forms, 5 to 7 minutes. Transfer to a plate. Wipe out skillet with a paper towel and brown remaining meatballs in remaining safflower oil.
Wipe skillet clean. Combine ketchup, remaining 2 tablespoons gochujang, vinegar, sesame oil, 1/2 cup water, and brown sugar in skillet; bring to a simmer over medium. Carefully add meatballs. Simmer, stirring occasionally, until sauce thickens slightly and meatballs are just cooked through and evenly coated, 6 to 8 minutes. Transfer to a shallow bowl, sprinkle with scallions and sesame seeds, and serve warm, with toothpicks.