Preheat the oven to 375 degrees F. Combine 1 tablespoon each olive oil and mustard, 1 teaspoon herbs, 1/2 teaspoon salt and a few grinds of pepper in a small bowl; rub all over the pork.
Line a baking sheet with parchment paper. Unroll the crescent dough onto a work surface (do not separate along the perforations). Arrange half of the Gruyere lengthwise down the center; lay the pork on top and wrap to enclose, pressing to seal. Transfer to the prepared baking sheet, seam-side down. Bake until golden and a thermometer inserted into the center reaches 145 degrees F, about 25 minutes. Let rest 5 minutes.
Meanwhile, combine the shallot, vinegar and the remaining 1/2 tablespoon mustard and 1 teaspoon herbs in a large bowl. Slowly whisk in the remaining 3 tablespoons olive oil until emulsified; season with salt and pepper. Add the greens, grapes and the remaining Gruyere; toss. Slice the pork and serve with the salad.
Photograph by Christopher Testani
Courtesy of Food Network Magazine