In a large mixing bowl, whisk together 1/4 cup white vinegar, 1/4 cup Dijon mustard, 2 cloves minced garlic, 1 teaspoon ground black pepper, 1 teaspoon salt, 1 teaspoon ground ginger, and 1/2 teaspoon cayenne pepper.

Add 4 chicken thighs to the marinade, toss to coat, and refrigerate for at least 30 minutes or up to overnight.

Heat 1/4 cup vegetable oil in a skillet over medium heat.

Add 2 large thinly sliced onions and sauté for 10-12 minutes until soft and golden brown.

Place the marinated chicken thighs in the skillet with the onions and cook for 5-7 minutes per side until browned and cooked through.

Pour any remaining marinade into the skillet and bring to a simmer over medium-low heat for 5 minutes to meld the flavors.

Check that the chicken reaches an internal temperature of 165°F and cook an additional 2-3 minutes if necessary.

Remove from heat, garnish with fresh parsley, and serve over rice or with crusty bread.