How to Make It
In a medium saucepan, bring the wine to a simmer and cook over moderate heat until reduced by half, about 3 minutes. Add the stock, peppercorns, bay leaf, garlic and a generous pinch of salt and return to a simmer. Add the chicken and cook over moderately low heat, turning the meat occasionally, until an instant-read thermometer inserted in the thickest part registers 160°, about 25 minutes. Transfer the chicken to a work surface and let cool completely before returning to the cooled poaching liquid.
In a medium saucepan, heat the olive oil. Add the onion, carrot and celery and cook over moderate heat, stirring occasionally, until the vegetables start to soften, about 5 minutes. Add the bacon and cook, stirring, until the fat is rendered but the bacon is not crisp, 3 to 5 minutes. Add 2 1/2 cups of water and bring to a boil. Stir in the lentils and season generously with salt and pepper. Simmer over moderate heat, stirring occasionally, until the lentils are just tender, about 20 minutes. Let the lentils cool in the liquid; drain. Using tongs, remove the onion, carrot and celery and discard.
In a small bowl, whisk the shallot with the lemon juice and vinegar and let stand for 5 minutes. Whisk in the mustard. Slowly drizzle in the olive oil and whisk until incorporated. Season the vinaigrette with salt and pepper. In a large bowl, toss the watercress with the almonds, dill and 1/4 cup of the vinaigrette.
In a bowl, toss the lentils with 1/4 cup of the vinaigrette and season with salt and pepper. Remove the chicken from the poaching liquid and transfer to a work surface. Slice the chicken, arrange on plates and drizzle with the remaining vinaigrette. Serve the lentils and watercress alongside.