In a small bowl, whisk together the honey, chicken stock, Dijon mustard, wholegrain mustard, white vinegar, sriracha, and fresh lemon juice until well combined and smooth. Set aside. I like to make this first so the flavors can start melding while you prepare the chicken—it makes a more cohesive sauce by the time it goes into the oven.
Pat the chicken dry with paper towels and cut into 1-inch pieces. In a small bowl, combine the smoked paprika, mustard powder, garlic powder, cayenne pepper, kosher salt, and ground black pepper. Toss the chicken pieces with this spice mixture until evenly coated on all sides. While the chicken seasons, preheat your oven to 375°F. Drying the chicken first helps it brown better when seared.
Heat the olive oil in a large oven-safe skillet over medium-high heat until shimmering. Working in batches if necessary to avoid crowding, sear the seasoned chicken pieces for about 2 minutes per side until golden brown on the outside. The chicken doesn't need to be cooked through at this stage—we're building flavor and color before finishing it in the oven.
Pour the honey mustard sauce from Step 1 over the seared chicken in the skillet, stirring gently to coat all the pieces evenly. Scatter the fresh thyme leaves over the top. Transfer the skillet to the preheated 375°F oven and bake for 15–25 minutes, until the chicken reaches an internal temperature of 165°F when tested with a meat thermometer. I prefer to bake this uncovered so the sauce reduces slightly and the chicken develops a nice glaze.
Remove the skillet from the oven and let the chicken rest for 2–3 minutes before serving. This allows the juices to redistribute and keeps the chicken tender. Spoon any accumulated sauce over the top when plating.