Put 4 thick-cut bacon slices on a rack set on a baking sheet. Place in a cold oven, set the temperature to 400˚ F and bake 35 to 40 minutes, rotating the pan halfway through. Let cool, then cut each slice into 6 pieces.
Combine 3 tablespoons mayonnaise, 1 tablespoon yellow mustard, 2 teaspoons relish, 1 teaspoon celery salt, a few dashes of hot sauce and a pinch of pepper in a food processor. Add 2 chopped hard-boiled eggs; puree. Transfer to a piping bag with a star tip.
Pipe the egg mixture onto each bacon piece and top with paprika and chopped chives.