Peel and cut the baked potatoes into medium sized chunks. (This can be done a day in advance to save time). Place butter and onions in a large pot. Cook till onions are semi-clear. Reserve 2 cups of milk and pour the rest in the pot with the onions. Warm milk and while it is heating mix remaining milk with the flour, whisking till smooth. Whisk the milk/flour mixture into the heated milk, continuing to whisk till well blended and smooth (minus the onions of course). When milk has thickened add the potatoes, bacon, salt, pepper, and garlic. Finally mix in the sour cream just till melted inches. Garnish as desired.