1. Preheat the broiler and position an oven rack 8 inches from the heat. Melt the butter in a large skillet. Add the minced shallots and cook over moderately high heat until barely softened, about 1 minute. Add the asparagus, season with salt and pepper and cook over moderate heat, stirring occasionally, until crisp-tender and lightly browned in spots, about 5 minutes.
2. Transfer the asparagus to a medium gratin dish and spread the truffle fondue over them. Broil until golden and bubbling, shifting the dish for even browning, about 1 minute. Sprinkle with the tarragon and serve.