How to Make It
In a small skillet, toast the pine nuts over high heat, shaking the pan, about 3 minutes. Transfer the nuts to a cutting board; let cool, then coarsely chop. In a small bowl, mash the butter with the mustard, tarragon and pine nuts and season with salt and pepper.
Light a grill or preheat a grill pan. Brush the zucchini with the oil, season with salt and pepper and grill over high heat, turning once, until lightly charred and crisp-tender, about 5 minutes. Arrange the zucchini on a platter and top with the pine nut butter.