Heat 1 Tbsp of oil in a large, oven-safe skillet on high heat.
Sear the chicken thighs until golden brown on each side, about 3 minutes per side. Once seared, turn to medium heat, cover and cook until the chicken is done and an instant read thermometer measures 165 degrees F, about 7-9 minutes.
While the chicken cooks, place a steamer basket over a pot of water and bring to a boil. Once boiling, add in the broccoli, cover and cook until the broccoli is bright green and tender, about 2-4 mins. Drain and set aside.
Transfer the chicken to a cutting board and wipe out the pan. Heat the remaining 1 Tbsp of olive oil on medium heat and cook the leeks and the paprika until just softened, about 2-3 minutes.
Turn to medium low and add in 1/4 cup of then Parmesan cheese, the cheddar cheese, cream cheese, whipping cream, mayo, mustard and salt. Whisk until smooth and creamy. Once done, remove from heat.
Cut the chicken into small cubes and add it, along with the broccoli, into the pot, stirring to coat.
Sprinkle the remaining Parmesan over the casserole and bake until bubbly, about 15 minutes. Then, turn your oven to HIGH broil and broil until golden, about 2-3 minutes.
DEVOUR!
Video
Notes
You could also transfer this to an 8x8 inch pan if you don't want to cook it in the pan!