Place potato pieces in a pot and fill with cold salted (1/4 cup salt) water, just covering the potatoes. Bring to a boil over medium high heat and cook for 15-20 minutes or until fork tender and drain.
While potatoes are cooking, combine cream cheese, sour cream, dijon mustard and hot sauce in a food processor. Blend until smooth.
Mash potatoes in a large bowl using a potato masher or ricer. Add cream cheese mixture and fold into the potatoes until blended, creamy and smooth. Carefully fold in jumbo lump crab (making sure not to break up the lumps too much), season with salt and pepper.
Preheat oven to 425°F. Spoon potatoes into an oven-safe casserole dish or skillet and top with shredded cheese. Bake for 8-10 minutes or until cheese has browned slightly and is bubbly. Top with chopped chives before serving.