Roasted Onion Gratin w/ Cheddar & Bacon

medium yellow onions, cored and quartered lengthwise

olive oil

coarse salt and freshly ground black pepper,

unsalted butter

flour

+ 1/2 cups heavy cream

dry white wine, optional

grate (or a pinch) or two of fresh nutmeg

heaping 1/2 cup of sharp white cheddar

slices bacon, cooked, crumbled