Put an oven-safe pan on medium heat (this pan is for the pork) and preheat your oven to 425.
Cover your pot of potatoes and turn the burner for the potatoes on high.
Once the pan for the pork is heated, sear the pork on all sides, insert a probe thermometer into the thickest part of the thickest piece of meat, and slide the pan into the oven.
Put a grill pan or another sauté pan (for the asparagus) on the heated burner the pan for your pork was on. Keep the burner set to medium.
Once the pork has reached an internal temperature of 143, remove the pan from the oven, remove the pork from the pan and place the pork on a cutting board to rest for about 10 minutes.
Add the asparagus to the heated grill or sauté pan on the stove. Remember to toss every couple of minutes (will be in the pan for about 5 minutes total)
When the potatoes are tender, strain them (reserving some of the cooking liquid) and put them in a blender with the butter, milk, dijon, about 1/4 cup of reserved cooking liquid, and a pinch of salt. Blend that all until silky smooth, adding more cooking liquid a little at a time until it is close to the consistency of pudding.