In a large bowl, combine crabmeat, cream cheese, sour cream, mayonnaise, heavy cream and artichokes. Season with horseradish, lemon juice, garlic, and black pepper. Mix well and spread mixture into a 9x13 inch baking dish and sprinkle the white Cheddar cheese and Old Bay seasoning on top.
Bake in a preheated oven for 30 minutes or until warm and melted. Meanwhile, hollow out the loaves of sourdough bread. Reserving the bread removed.
Spoon the hot crab dip into the hollowed out loaves of sourdough. Use the reserved bread for dipping.
