Finely chop the onion, mince the garlic cloves, and cut the chicken breasts into 1-inch cubes. In a small bowl, combine the Italian seasoning, paprika, salt, black pepper, and red pepper flakes. Toss the chicken cubes with this spice mixture until evenly coated, ensuring every piece is seasoned. I like to do this step ahead of time so the chicken absorbs the flavors while you prep the rest of the components.

Heat the olive oil in a large skillet over medium heat. Add the chopped onion and cook for about 5 minutes, stirring occasionally, until it becomes soft and translucent. Add the minced garlic and cook for an additional minute until fragrant. This creates a flavorful base that will complement both the chicken and the honey mustard sauce.

Increase the heat to medium-high and add the spiced chicken cubes from Step 1 to the pan with the onion-garlic mixture. Cook for 3-4 minutes without stirring too much, allowing the chicken to develop a golden-brown crust on one side. Turn the chicken pieces and cook for another 2-3 minutes until the second side is browned. The chicken won't be completely cooked through at this point, which is intentional—it will finish cooking in the sauce.

While the chicken is searing, whisk together the Dijon mustard, coarse grain mustard, honey, and chicken broth in a small bowl until well combined. Once the chicken has browned on both sides, pour this sauce mixture over the chicken and onions in the skillet. Stir gently to coat everything evenly and bring the sauce to a simmer.

Reduce the heat to medium and let the chicken simmer in the honey mustard sauce for 2-3 minutes, stirring occasionally, until the chicken is cooked through and the sauce has thickened slightly. The internal temperature of the chicken should reach 165°F. Transfer to a serving platter and garnish with fresh chopped parsley. I find that letting it rest in the sauce for just a couple of minutes helps the flavors meld together beautifully before serving.