Start by patting the boneless, skinless chicken thighs dry with paper towels to ensure a nice sear. In a Dutch oven, heat 2 tablespoons of olive oil over medium-high heat. Once shimmering, add the chicken thighs and sear them for 2-3 minutes per side until golden brown. Remove the chicken and set it aside on a plate.

In the same Dutch oven, add the chopped onion and sauté for about 5 minutes, stirring occasionally, until translucent and fragrant. Then, add the minced garlic and cook for an additional minute, ensuring it doesn't burn.

Next, stir in the ketchup, packed brown sugar, apple cider vinegar, Worcestershire sauce, smoked paprika, dry mustard, salt, and black pepper. Mix well and bring the sauce to a gentle simmer. Let it bubble for about 2-3 minutes to meld the flavors.

Return the seared chicken thighs to the pot, making sure they are submerged in the BBQ sauce. Lower the heat to a gentle simmer and cover the pot. Cook for 2-3 hours on the stovetop, or transfer to a slow cooker and cook for 4-6 hours.

Once the chicken is fork-tender, remove it from the pot and transfer it to a cutting board. Use two forks to shred the chicken into bite-sized pieces.

Preheat your oven to 400°F (200°C). Spread the shredded chicken evenly on a parchment-lined baking sheet. Bake for 15-20 minutes, stirring halfway through, until the edges become crispy.

Remove the chicken from the oven and return it to a bowl. Garnish generously with chopped fresh parsley and serve warm.