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1
Preheat oven to 325 degrees F (165 degrees C).
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2
Combine kosher salt, black pepper, Italian seasoning, dried rosemary, granulated garlic, granulated onion, and lemon pepper together in a small bowl.
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3
Place lamb in a large roasting pan. Rub with lemon juice, 1 tablespoon olive oil, red wine, and Worcestershire sauce on all sides and between any crevices. Sprinkle with kosher salt mixture and rub over all sides. Pour white wine, chicken stock, 4 crushed garlic cloves, bay leaves, capers, and anchovies into the bottom of the roasting pan.
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4
Cover pan tightly with heavy-duty aluminum foil and roast lamb in the preheated oven until tender but still pink in the center, 1 1/2 to 2 hours. An instant-read thermometer inserted into the center of the meat should read 130 degrees F (54 degrees C).
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5
Remove lamb to a cutting board and allow to cool slightly before slicing. Transfer meat to a large bowl and toss with some of the pan juices to keep it moist. Reserve remaining pan juices.
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6
Increase oven temperature to 500 degrees F (260 degrees C).
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7
Mix sour cream, horseradish, mustard, and garlic basil spread in a small bowl until combined. Cover and refrigerate.
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8
Heat 2 tablespoons olive oil in a large pot or Dutch oven over medium-high heat; cook and stir onions until they soften and begin to turn golden, about 12 minutes. Pour in Marsala wine and cook until reduced, about 5 minutes.
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9
Stir mushrooms, Kalamata olives, 2 tablespoons minced garlic, fresh rosemary, and red pepper flakes into onion mixture; cook and stir until mushrooms have softened, about 5 minutes. Add lamb slices and reserved pan juices. Cook, stirring to combine, until heated through, about 10 minutes.
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10
Spread each hoagie bun with horseradish sauce. Spoon lamb mixture into buns and top each sandwich with 1/4 of the lettuce, cherry tomatoes, Asiago cheese, and feta cheese. Serve with remaining pan juices for dipping.
