Put the potatoes in a medium saucepan of salted water. Bring to a boil. Lower the heat; simmer until almost tender; about 5 minutes.

In a large nonstick or cast iron frying pan, cook the bacon until crisp. Remove the bacon from the pan and crumble it. Pour off and reserve all but 1 tablespoon of the fat from the pan. Add the onion to the pan and cook over moderate heat, stirring frequently, until browned, about 8 minutes. Remove the onion. Wipe out the pan.

In the same pan, heat the reserved bacon fat and enough oil to measure 3 tablespoons over moderately high heat. Add the potatoes; let them cook, without stirring, for 6 minutes. Add .25 teaspoons of the salt, stir, and cook the potatoes until well browned, about 6 minutes longer. Add the onion and bacon and continue cooking until they are warm through, about 1 minute longer.

In a medium saucepan, heat the cream cheese, milk and Worcestershire sauce, cayenne, and the remaining .25 teaspoon salt over moderately low heat, stirring, until hot, about 5 minutes. Add the crab and black pepper and cook, stirring, until warm through, about 2 minutes longer. Stir the crab mixture and 2 tablespoons of the chives into the potatoes until just combined. Serve topped with the remaining 1 tablespoon chives.