Blanch and peel the onions up to 2 days in advance; cook the bacon up to several hours ahead. Brown the onions just before serving.
3 pounds pearl onions
4 thick strips bacon, coarsely chopped
1 tablespoon reserved bacon fat
1 tablespoon butter
1 tablespoon balsamic vinegar
2 tablespoons chopped fresh thyme
Bring a large saucepan of water to a boil. Add the onions and cook for 2 minutes. Drain the onions into a colander and rinse them with cold water.
When the onions are cool enough to handle, use a paring knife to slice off the root ends, leaving the pointed ends and most of the root intact. Using your hands, slip the papery skin off the onions and discard it. Continue until all the onions are peeled.
In a skillet, render the bacon over medium heat, turning often, until it is golden brown. With a slotted spoon, transfer it to a plate lined with paper towels. Discard the fat, reserving 1 tablespoon.
Heat the bacon fat. Add the butter, and when it melts, add the onions. Cook over medium heat, stirring often, for 20 minutes or until the onions are caramelized. Stir in the vinegar and thyme. Turn the heat to low and continue cooking for 5 minutes. Add the reserved bacon, heat it through, and serve at once. Sheryl Julian and Julie Riven.