Preheat the oven to 350 F.In a small skillet, sweat the onions over medium-low heat in the butter or olive oil until they are soft and translucent, about 5 minutes.
Add the garlic and cook for another minute then remove from the heat and allow to cool.In another skillet, saut the bacon over low heat until soft and the fat is beginning to render out, but dont allow it to brown.
Remove to a paper towel and set aside.
Place the chicken breasts between two sheets of waxed paper and evenly pound to 1/4-inch thickness, either with the smooth side of a meat mallet or a small, heavy pan. Season on both sides with the salt and pepper.Stir the onion and garlic into the cream cheese until well blended; divide evenly between the chicken by placing a dollop in the center of each breast.
Roll or fold the chicken around the cream cheese mixture, tucking the ends under and securing with toothpicks.
Sprinkle the tarragon evenly over the chicken packages, and wrap each with a piece of bacon.
Place in an 8x11 baking dish and drizzle with the melted butter.
Bake for 25 to 30 minutes, or until the chicken is done, the bacon is browned and the cream cheese is heated all the way through.
