Chicken and Shallot Jam on Pain au Levain

1. 1
   Place all the ingredients in a medium saucepan. Cover with cold water by 1 to 2 inches and bring to a simmer over medium-high heat; reduce heat to medium low and simmer gently until the chicken is completely cooked and no longer pink in the center, about 20 minutes. Remove the chicken from the poaching liquid to a cutting board and let cool to room temperature. Meanwhile, make the shallot-tarragon jam.

For the shallot-tarragon jam:

1. 1
   Heat the oil and butter in a large frying pan over medium heat until the butter is foaming.
2. 2
   Add the shallots, salt, and pepper and cook, stirring occasionally, until the shallots are softened and just beginning to brown, about 10 minutes.
3. 3
   Stir in 1/4 cup of the vinegar and the sugar and cook, stirring occasionally, until the shallots are completely soft and caramelized and the jam is thick and syrupy, about 20 to 25 minutes.
4. 4
   Remove the pan from heat and stir in remaining 2 tablespoons of vinegar. Let the jam cool for 20 minutes, then stir in the chopped tarragon.

To assemble the sandwiches:

1. 1
   Slice the chicken into 1/4-inch thick pieces.
2. 2
   Evenly divide the shallot jam on 1 side of 4 slices of the bread. Divide the chicken evenly among the sandwiches, placing it on top of the jam in an even layer. Close each sandwich and serve.