Preheat the oven to 375F.
Place the chicken breasts on a cutting board and cover with parchment paper or plastic wrap. Using a meat mallet or the bottom of a heavy skillet, pound the chicken until it is a uniform ½-inch thickness. Pat dry with paper towels.
Season both sides of the chicken evenly with the salt, pepper and smoked paprika.
Add the cassava flour to a shallow bowl and dredge both sides of the chicken into the flour so that it evenly coats all over. Shake off excess.
Heat the oil in a large, oven safe skillet over medium-high heat. Add the chicken and cook until golden-brown on both sides, 2 to 3 minutes per side. Transfer the browned chicken to a clean plate and set aside.
Reduce the heat to medium, add the onion, mushrooms and garlic and cook, stirring, until tender, 5 to 7 minutes.
Stir in the dijon and fresh thyme until combined. While stirring, add the white wine and broth and stir until well combined.
Nestle the chicken back into the skillet and top with the gruyere cheese. Transfer to the oven and bake until the chicken is cooked through and the cheese is lightly browned and bubbly, about 10 minutes.
Remove from the oven, serve and enjoy!