4 tablespoons unsalted butter, at room temperature, plus 1 1/2 tablespoons, melted
Freshly ground pepper
1 ounce Roquefort cheese, at room temperature
4 large baking potatoes
Peanut oil, for deep-frying
Coarse sea salt
Brush the steaks with the melted butter and season with pepper; let the steaks come to room temperature.
In a small bowl, beat the 4 tablespoons of butter with the Roquefort until blended.
Peel the potatoes and slice lengthwise 1/4 inch thick. Cut the slices into 1/4-inch-wide sticks and soak in ice water for 15 minutes.
In a deep-fryer or a large saucepan, heat 2 inches of oil to 325°. Drain the potatoes and blot them completely dry. Divide the potatoes into 4 batches and fry each batch until cooked through but not browned, 4 to 6 minutes. Using a slotted spoon, transfer the fried potatoes to paper towels to drain.
Light a grill. Generously season the steaks with salt and grill over a hot fire for 4 to 6 minutes per side for medium rare. Alternatively, pan-fry the steaks over moderately high heat for about 4 minutes per side.
Reheat the oil to 375°. Fry the potatoes until crisp and golden brown, 1 to 2 minutes per batch. Using a slotted spoon, transfer the frites to fresh paper towels to drain. Top each steak with a spoonful of Roquefort butter and serve the frites on the side.