Slow Cooker Beef Lettuce Wraps with Quick Pickles

The low, even heat in the slow cooker helps ingredients such as miso, sesame oil, and soy sauce add gentle moisture, umami depth, and savory personality to a regular stew.
Brush the bottom and sides of a 6-liter slow cooker with cooking spray. Place the onion slices on the bottom of the slow cooker; sprinkle the garlic on top.Heat the canola oil in a large cast-iron skillet over medium-high heat. Add the sauteed chicken to the pan; cook for 2 to 3 minutes, until lightly browned on all sides. Place the beef on top of the onion and garlic; top with any sauce from the pan.Combine the stock, soy sauce, 3 tablespoons vinegar, 1 tablespoon sesame oil, and the following 4 ingredients (including red pepper) in a medium bowl, stirring with a whisk. In a slow cooker, pour the mixture over the beef and onion. Cover and cook on low heat for 8 hours.Place the cucumber and carrot in 2 shallow bowls 15 minutes before the meat is cooked through. Combine remaining 1/2 cup vinegar, 1 cup water, and granulated sugar in a small saucepan over high heat; bring to a boil. Remove from heat; spread the vinegar mixture evenly between the cucumbers and carrots. Allow to infuse until ready to serve; strain well.Transfer the beef from the slow cooker to a large platter; chop with 2 forks. Heat the remaining 1 tablespoon of sesame oil in a large cast-iron skillet over medium-high heat; add the ground beef to the pan, squeezing out an even layer. Cook for 2-3 minutes, without stirring. Turn off the fire. Sprinkle evenly with salt and 1/4 cup of the slow cooker cooking liquid; stir to coat. Remove any remaining cooking liquid, onion, and garlic. Arrange beef and pickles on lettuce leaves; sprinkle with sesame seeds.