3 tbsps prepared mustard
3 to 3-1/2 pounds beef short ribs, excess fat trimmed
1/3 cup all-purpose flour
1/4 cup extra virgin olive oil
4 leeks (white part only), sliced
1/3 cup chopped fresh parsley
1 cup crushed canned tomatoes
1-1/2 cups chicken broth
1/4 cup sherry
1 tbsp brown sugar, packed
1-1/2 tsp salt
1/2 tsp pepper
1 tbsp fresh tarragon
6 carrots, cut into 2-inch pieces
6 medium-size potatoes, peeled and cut into 1/2-inch slices
1/4 cup sour cream
1/4 cup butter, softened
1-1/2 tbsps flour

Brush mustard on surface of beef short ribs. Place flour in a shallow dish. Coat ribs with flour, shaking to remove excess. In a pressure cooker, heat oil. Add ribs and sauté in hot olive oil, turning to brown on all sides. Remove and set aside. Add leeks and parsley and saute in hot oil 2 minutes. Stir in tomatoes, broth, sherry, brown sugar, salt, pepper, and tarragon. Add ribs. Secure lid. Over high heat, develop steam to high pressure. Reduce heat to maintain pressure and cook 18 minutes. Realease pressure and remove lid according to manufacturer's directions. Add carrots and potatoes to rib mixture. Secure lid. Over high heat, develop steam to high pressure. Reduce heat to maintain pressure and cook 6 minutes. Release pressure according to manufacturer's directions. Remove lid. Transfer ribs and vegetables to a platter. Combine sour cream, butter, and flour, blending until smooth. Gradually add to cooking liquid, stirring and cooking over medium heat 1 minute. Spoon sauce over ribs and vegetables.