1 boneless corned beef brisket with seasoning packet (3-1/2 to 4 pounds)
6 cloves garlic, peeled
2 teaspoons whole black peppercorns
2 cups water
6 tablespoons butter
1 cup thinly sliced green onions, including white and green parts
1/2 cup horseradish
1/2 teaspoon ground black pepper
1/4 teaspoon salt
1 head green cabbage, cored, cut into 6 wedges (1 to 1-1/2 pounds)
1-1/2 pounds small red-skinned potatoes, cut in half
2 tablespoons orange marmalade
2 teaspoons Dijon-style mustard
Position oven racks in upper and lower thirds of oven. Heat oven to 350°F. Place corned beef brisket in roasting pan; sprinkle garlic, contents of seasoning packet and peppercorns around and over brisket. Add water; cover tightly with aluminum foil. Braise in upper third of 350°F oven 3 to 3-1/2 hours or until brisket is fork-tender.
Meanwhile, place butter, green onions, horseradish, ground pepper and salt in glass measuring cup. Microwave on HIGH 1 to 2 minutes or until butter melts; mix well. Cover and refrigerate 2 tablespoons for Rustic Corned Beef & Potato Bake <http://www.beeftips.com/rusticcornedbeefandpotatobake.aspx>. Place cabbage wedges on 1 half of baking sheet and potatoes on other half. Drizzle remaining horseradish-butter mixture over vegetables, turning cabbage and tossing potatoes to coat. Cover with aluminum foil. Roast in lower third of 350°F oven with brisket 55 minutes. Uncover vegetables; continue roasting 15 to 20 minutes or until vegetables are tender and begin to brown.
Combine glaze ingredients in small bowl. Remove brisket from roasting pan; place on rack in broiler pan so surface of brisket is 3 to 4 inches from heat. Brush glaze over brisket; broil 2 to 3 minutes or until glaze is bubbly and beginning to brown.
Carve brisket diagonally across the grain into thin slices and serve.