Preheat the oven to 375°F (190°C). Heat a heavy skillet over medium-high heat; coat lightly with cooking spray. Season the steaks with 1/8 tsp (0.5 ml) each salt and pepper and sear in the skillet for 1 to 2 min. on each side. Transfer steaks to a parchment paper-lined baking sheet and brush the mustard evenly onto the tops. Mix the parsley and 2 tsp (10 ml) tarragon together and press onto the mustard. Roast for 10 min. for medium (160°F/71°C on an instant-read thermometer).
Meanwhile, place the peas, garlic and 1/2 cup (125 ml) water in a medium saucepan over medium-high heat, cover and bring to a boil. Remove from heat and purée with a hand-held blender until creamy but still studded with pieces of peas. Transfer to a bowl and stir in the sour cream, lemon juice and zest and the remaining tarragon, salt and pepper. Divide the peas and steaks among 4 plates and serve.
A steak dinner with only 4.5 grams of fat and 250 calories per serving