Layer the potatoes in the bottom of the slow cooker insert. Then layer all the eggplant slices on top.
Grind the cinnamon, cloves, peppercorns and allspice to a powder in an electric spice mill or mortar and pestle.
In a large saute pan, heat the oil and cook the onion until it begins to brown, about 7 minutes. Add the garlic, spices, wine, tomatoes, and artichokes and continue to simmer until the pan is nearly dry. Add salt to taste.
Pour the tomato-artichoke sauce carefully over the eggplant and potatoes (this dish can be assembled to this point a day ahead of time and stored in the refrigerator overnight). Cover and cook on low for about 4 hours, or until a skewer inserted into the stew easily penetrates all the layers.
While the vegetables are cooking, make the custard topping. Combine the milk and flour in a blender and blend until smooth. Pour the mixture into a saucepan and cook over medium-high heat, stirring constantly, until the sauce thickens enough to thickly coat the back of a spoon. Gradually stir in the cheese, then turn off the heat and rapidly whisk in the egg yolks one at a time. Stir in a dash of nutmeg.
Carefully pour the custard over the vegetables, trying not to dislodge them. Cover and continue cooking for about 1 hour longer, or until the custard is set.
Turn off the slow cooker and let the moussaka sit for 15-20 minutes, then carefully spoon up individual portions into a pasta bowl. Tip: The recipe suggests slicing up the dish into 4-6 portions right in the slow cooker insert with a sharp knife before removing the portions with a spoon.