Tarragon Chicken with Spring Greens

Name: Tarragon Chicken with Spring Greens
Ingredients: 2 tablespoons unsalted butter; 1 tablespoon canola oil; 8 chicken thighs (6 ounces each); Salt; Freshly ground pepper; 5 ounces baby arugula, cut into ribbons; 1 head of romaine lettuce, cut into ribbons; 1 bunch of watercress— thick stems discarded, the rest coarsely chopped; 1 leek, halved lengthwise and thinly sliced crosswise; 3 tablespoons finely chopped tarragon; 1 teaspoon caraway seeds; 3/4 cup dry white wine; 1/2 cup low-sodium chicken broth; 4 ounces crème fraîche; Steamed rice, for serving