Preheat the oven to 375 degrees. Slice the chicken in half about 3/4 of the way. Open the chicken and pound each side to be about 1/4 inch thick.: The kitchen warms as you preheat the oven, and that steady, even heat is what finishes the chicken without drying it out. You should notice the oven light comes on and a faint warmth in the room, signaling readiness. I like to set a timer as soon as I turn the dial so I do not forget. A common mistake is putting meat into an oven that is not fully warmed; this can lengthen cooking time and affect texture.
Stuff the chicken breasts each with 2 slices of cheese, and 3 asparagus stalks. Fold the chicken over and secure it with toothpicks around the edges.: When you open the chicken , you can hear and feel the meat separate as you create a pocket. This technique allows the breast to hold filling without being cut in two. After slicing, lay the breast flat on a cutting board and gently pound each side to about 1/4 inch thick, which evens thickness and ensures even cooking. Use light, measured blows so you avoid tearing the meat; pounding too hard can create holes that let the filling escape.
In a small bowl combine the brown sugar, chili powder, paprika, Italian seasoning, garlic powder, salt, and pepper. Rub generously on each side of the chicken.: As you place the Mozzarella Cheese and Asparagus inside, you will see how the textures contrast, and the cheese will begin to cling to the stalks. Fold the chicken over and secure it with toothpicks around the edges to keep everything snug. If the filling is cold it holds together better, so I sometimes chill the asparagus briefly. Be careful not to overstuff, which can force the seams open during cooking.
Add the olive oil to a medium-sized skillet and turn to medium-high. Add the chicken and sear on each side for 2-3 minutes. Cover the pan with foil and put it into the oven. Cook for about 15-20 minutes or until the chicken is cooked throughout.: The spices release aroma as you mix them, and the sugar binds lightly to the blend, creating a crusting effect when rubbed on. I work the mixture with a spoon until it's uniform and fragrant. Rub this seasoning generously on each side of the stuffed chicken , pressing so it adheres. Watch that you do not add too much salt for a balanced finish, and if your chili powder is particularly pungent, apply with restraint to avoid an overly hot bite.
Add the olive oil to a medium-sized skillet and turn to medium-high: The pan should hiss gently when the oil starts to shimmer, which signals it is hot enough to sear. Add the stuffed chicken and sear on each side for 2 to 3 minutes, watching for a golden brown crust to form and an enticing sizzling sound. This sear locks in juices and creates a savory outer layer. If the pan is too crowded, steam can form instead of a crust, so sear in batches if needed. A common pitfall is not heating the pan enough, which prevents proper browning.
Cover the pan with foil and put it into the oven: The foil traps heat and gently finishes the cooking while keeping moisture in, so the filling melts without drying. Slide the skillet into the preheated oven and let the residual heat do the work. Cook for about 15 to 20 minutes or until the chicken is cooked throughout, checking for an internal doneness that feels firm but springy to the touch. A thermometer is helpful; aim for a safe internal temperature. Avoid leaving it too long, which can result in dry meat; better to check early and add a couple of extra minutes if needed.
