Place sun-dried tomatoes in a bowl; pour boiling water over them and let steep until softened, about 10 minutes. Drain and chop.
Mix boursin cheese with scallions and set aside.
Cut a horizontal slit along the thin, long edge of each chicken breast, nearly through to the opposite side, and open like a book.
Sprinkle the breasts with 1/4 teaspoon each salt and pepper.
Divide the cheese filling among the breasts, placing it in the center of each. Top with spinach and sun-dried tomatoes. Close the breast over the filling, pressing the edges firmly together to seal.
Sprinkle the breasts with paprika, 1/4 teaspoon salt and pepper.
Heat oil in a large ovenproof skillet over medium-high heat. Add the chicken and cook until browned on one side, about 2 minutes. Turn the chicken over and transfer the skillet to the oven. Bake until the chicken is no longer pink in the center, about 15 minutes.