Place bacon fat in a medium pan over medium-low heat. Add shallots; cook 1 minute. Remove from heat; stir in vinegar, tarragon, sugar, salt, and pepper. Use dressing immediately; it will dress 6 cups of greens.
Rendering Bacon Fat
Cooking bacon over low heat melts the solid fat, rendering it from the meat. It's so versatile, and a little goes a long way, so it's our tactic for bringing a smoky presence to a dish without adding a lot of fat.
Cut up the bacon. Rather than cooking full strips, use kitchen shears to snip cold bacon into 3/4-inch pieces. The small pieces will fully cover the pan and render evenly.
Choose the right pan. Select a pan that lets the bacon cook evenly, immersed in its own fat, without burning. Use a small pan for 3 ounces of bacon, a medium skillet for 6 to 8 ounces, and a large skillet for more.
Employ gentle heat. Cook bacon over medium-low heat 10 minutes or until the fat is released and the meat is crisp and browned.
Strain and go. Filter out the gritty browned bits--they can taste bitter. Use bacon fat to add smoky flavor to sautéed vegetables, soups, and croutons. Or use it to make a vinaigrette, like this one.