Move an oven rack to the middle position and preheat the oven to 400°F. Heat your cast-iron or oven-friendly skillet to medium-high heat and add extra-virgin olive oil. Add diced chicken, season with smoked paprika, salt and pepper, and sear until browned on all sides. Remove the chicken from the skillet and set aside. (Your chicken is not cooked through yet—it will finish safely in the simmering liquid later.)
Reduce heat to medium and add the diced onion to the skillet. Sauté until translucent, about 4-5 minutes. Add minced garlic and cook until fragrant, about 30-45 seconds. Add the whole wheat orzo and sauté for another minute to lightly toast the pasta, enhancing its flavor.
Add the broccoli, seared chicken, chicken stock, and milk. Bring the mixture to a low boil, then reduce heat, cover, and simmer for 5 minutes. Stir in about half of the shredded cheese and simmer for another 5 minutes until the cheese is melted and the pasta is nearly al dente (firm to the bite). Turn off the stove and remove from heat.
Top the skillet with the remaining cheese and bake in the preheated oven until the cheese is melted and bubbly (about 5-8 minutes). Top with whole wheat panko bread crumbs (optional), return to the oven for 2 minutes to crisp the topping, and serve.