Thinly slice the onions. Add the butter to a cast iron skillet. Melt the butter over medium low to medium heat. Pour the onions in. Add the sugar, white wine or sherry, garlic, salt, pepper and spice. Cook over medium heat stirring every few minutes for the first half hour. During the next half hour, stir very frequently, almost constantly, until the onions are soft and deep golden with no white left. This will take about another half an hour.

When the onions are caramelized, remove them from the heat and let them cool enough to work with.

Preheat the oven to 400.

Cut a sturdy loaf of bakery bread like sourdough in a grid pattern as shown. Don't cut all the way through the bread but leave each end attached to the bottom crust of the bread.

Once you've cut the pattern into the bread, spoon butter into the crevices. Then stuff the onions into all the crevices, using a spoon to gently push it down as much as you can. Next gently stuff shredded cheese into the crevices.

Bake in a preheated 400 degree oven for 10 minutes or until the cheese is melted.