Cook 4 chopped bacon strips until crisp. Drain on paper towels, reserving the drippings. Combine 4 egg yolks, 3 tablespoons water, 1 tablespoon white wine vinegar, 1 teaspoon Dijon mustard and a pinch of cayenne in a heatproof bowl set over simmering water; whisk until thick, 4 minutes. Remove from the heat and whisk in 1 tablespoon bacon drippings, and salt to taste. Serve over steamed asparagus and top with chives and the bacon.