Toss artichoke hearts with lemon juice in small bowl. Let stand for 10 minutes. Sauté garlic in olive oil in skillet til browned. Discard garlic. Drain artichoke halves. Add to skillet with the parsley. Sauté til lightly browned. Stir in flour.
Add crème fraiche and whipping cream gradually, stirring constantly. Season with salt and pepper. Cook just til steaming but not boiling. Spread cooked spaghetti in baking dish. Add artichoke mixture and toss to combine. Top with the cheese and dot with the butter. Bake in a preheated 400 oven for 15 minutes. Serves 8 to 10