Instructions

Melt 2 tablespoons unsalted butter in large saucepan over medium-high heat. Add 1 finely chopped small onion and ¾ teaspoon table salt and cook until softened, 3 to 5 minutes. Stir in 5 cups frozen cooked rice and 1 cup chicken broth and cook, stirring frequently, until rice is warmed through, about 6 minutes. Stir in 1 cup mascarpone. Remove from heat and cover until ready to serve.
Meanwhile, pat 4 trimmed filets mignons dry with paper towels and sprinkle with ¾ teaspoon pepper and 1 teaspoon salt. Melt 1 tablespoon butter in 12-inch nonstick skillet over medium-high heat. Add steaks and cook until meat is well browned and registers 120 to 125 degrees (for medium-rare), 4 to 5 minutes per side. Transfer to platter.
Melt 2 tablespoons butter in now-empty skillet over medium heat. Add 1 pound radishes, trimmed and quartered, and remaining ¼ teaspoon salt and ¼ teaspoon pepper and cook until radishes are lightly browned and crisp-tender, 7 to 10 minutes, stirring halfway through cooking.
Whisk 2 tablespoons lemon juice, 1 teaspoon flour, and remaining ½ cup chicken broth together in bowl, then add to skillet, scraping up any browned bits. Bring to simmer over medium-high heat and cook until thickened and bubbling throughout, 2 to 4 minutes. Off heat, stir in 3 tablespoons minced parsley, 1 teaspoon grated lemon zest, and remaining 1 tablespoon butter. Season with salt and pepper to taste. Slice steaks and serve with rice and radishes.