How to Make It
Preheat the oven to 350°. Spread the duck skin and fat in a pie plate and bake for about 15 minutes, until crisp. Drain on paper towels, then break into pieces.
Meanwhile, spread the walnuts in a pie plate and toast for 8 minutes; coarsely chop.
In a large bowl, mix the vinegar with the mustard and shallot. Gradually whisk in the walnut and vegetable oils. Season generously with salt and pepper. Add the frisée, Boston lettuce and walnuts and toss to coat. Top the salad with the raspberries, sliced duck breast and cracklings and serve.