Reduced-fat milk and light cream add richness to the pepper sauce minus the cals.
Preheat oven to 240C/220C fan forced. Line a baking tray with baking paper. Bring a saucepan of salted water to the boil over high heat. Add potato. Cook for 5 minutes or until just tender. Drain well. Pat dry with paper towel. Transfer to prepared tray. Drizzle with 1 tbs of the oil. Season with sea salt. Bake, turning halfway through cooking time, for 25 minutes or until golden. Keep warm in oven.
Reduce oven to 180C/160C fan forced. Line baking tray with baking paper. Spray the beef with olive oil and season. Heat a large non-stick frying pan over medium-high heat. Cook beef, turning, for 3 minutes or until browned. Transfer to prepared tray. Roast for 8 minutes for medium or until cooked to your liking. Set aside for 5 minutes to rest.
Meanwhile, heat remaining oil in frying pan over medium-low heat. Cook shallot and thyme, stirring, for 2 minutes or until soft. Stir in wine for 1 minute or until almost evaporated. Stir in stock and peppercorns. Simmer for 4 minutes or until reduced slightly. Combine milk, cream and cornflour in a bowl. Stir into stock mixture for 2 minutes or until sauce thickens.
Stir resting pan juices into sauce. Season. Discard thyme. Serve sauce over steaks with chips and beans.