Do your best to choose onions that are uniform in size for even cooking. If you don't want to use white wine, you can easily substitute chicken broth. You can also top each onion with a bit of shredded cheese - muenster is a personal favorite.
Trim a slice, about 1/2-inch thick, from the root end of each onion. Peel away the papery skin and place the onions in a covered, microwave-safe dish with about 1/4-inch of water in the bottom. Microwave at 80% power for 4 to 4-1/2 minutes. Remove from the oven, drain off the water and let stand, uncovered, until cool enough to handle.
To begin removing the inner layers of the onion, insert a fork into the center through the cut end, about 1-inch deep. Twist to separate the layers, pull upward gently, remove and set aside. Repeat with additional layers until you are left with a hollow shell about 3/8-inch thick. This could be one or two remaining layers, depending on your onion.
Chop the reserved onion into 1/2-inch dice. Melt the butter in a large pan over medium heat. Add the onions and cook until softened completely, about 2 minutes. Season with salt and pepper, then sprinkle the flour evenly over the onions, tossing to coat. Continue to cook, stirring constantly, until the flour begins to turn uniformly golden in color, about 3 minutes. Slowly add the white wine and stir to combine thoroughly. Stir in the half-and-half and continue cooking until the mixture is thickened and smooth, about 3 additional minutes. Taste and adjust the seasoning if desired
Using a spoon, fill the onion shells with the creamed mixture, pressing down gently with each spoonful. Top with the breadcrumbs, dust with a bit of paprika for color, and place in the oven for 8 to 10 minutes, or until the crumbs have browned.