Cover Cabbage With Boiling Water And Let Stand For 10 Minutes. Mix Pork, Onion, Rice, Mustard, Salt, And Pepper. Cook In Dutch Oven Until Pork Is Done. Drain Grease. Place Quarter Cup Of Meat Mixture Into Each Cabbage Roll. Secure With Toothpicks. Place In Dutch Oven With Seam Side Down. In A Bowl, Combine Tomatoes, Brown Sugar, Vinagar, Allspice, And Salt. Pour Over Cabbage Rolls. Heat To Boiling, Reduce Heat, Cover And Simmer 30 Minutes. Remove Rolls, Keep Warm, Stir In 1/4 Cup Cold Water And Cornstarch. Cook Until Mixture Boils, Stirring Constantly. Spoon Over Rolls And Serve.