Prime Rib Dip Recipe

Prepare meat and base

Slice cooked prime rib thinly against the grain into 1/8"–1/4" slices. Keep warm covered with foil. Reserve any pan juices.

Saute aromatics

In a medium saucepan over medium heat, melt 2 tbsp beef drippings or butter. Add smashed garlic and thyme sprigs; cook 30–45 seconds until fragrant but not browned.

Deglaze and simmer

Add 1 cup red wine (or extra broth) to deglaze, scraping any browned bits from the pan. Reduce by half, 2–3 minutes. Add 3 cups beef broth, 1 tsp soy sauce, and 1 tbsp Worcestershire. Bring to a gentle simmer.

Season and finish

Simmer uncovered 8–10 minutes to concentrate flavor. Season with 1/2 tsp salt and 1/4 tsp black pepper. If you prefer a slightly thicker jus, whisk 1 tsp cornstarch with 1 tbsp water to make a slurry, then slowly whisk into simmering jus and cook 1–2 minutes until slightly thickened. Remove garlic and thyme. Keep warm; transfer to a shallow bowl for dipping when serving.

Combine 1/4 cup prepared horseradish, 1/4 cup mayonnaise, 2 tbsp sour cream, 1 tsp Dijon mustard and 1 tsp lemon juice in a small bowl. Season with 1/4 tsp salt and 1/8 tsp black pepper. Taste and adjust—add more horseradish for heat or more mayo/sour cream to mellow. Chill until service.

Heat 1 tbsp butter and 1 tsp olive oil in a wide skillet over medium-low heat. Add 2 cups thinly sliced yellow onion and 1/8 tsp salt. Cook, stirring occasionally, 20–30 minutes until onions are deeply golden and sweet; if they cling or cook too slowly, add 1/2 tsp brown sugar to encourage caramelization. During the last 1–2 minutes, stir in 1 tsp balsamic vinegar to finish. Remove from heat and keep warm.

Preheat broiler (or oven to 450°F/230°C). Slice baguette into sandwich-length pieces and split. Lightly butter cut sides with 1 tbsp butter.

Arrange baguette halves cut-side up on a baking sheet. Layer Swiss cheese slices on the bottom halves. Warm 1.2 lb sliced prime rib in a skillet for 1–2 minutes with a splash of the prepared au jus to heat through (or briefly under the broiler). Pile warmed prime rib onto the cheese-topped halves; spoon caramelized onions over the meat.

Broil 1–2 minutes until cheese melts and bread edges are toasted—watch closely to prevent burning. Remove from oven.

To serve, place top half of baguette on sandwich, slice into portions. Serve each sandwich with a small bowl of au jus for dipping and a dollop or ramekin of creamy horseradish on the side. Optionally, allow diners to spoon horseradish inside the sandwich before dipping.