Place your eggs in a medium saucepan. Fill the pan with water going about 1 inch above the eggs. Bring to a boil and reduce heat slightly to prevent having the eggs crack. Gently boil for 7 to 8 minutes. Take the eggs out of the hot water and transfer to an ice bath. Once cooled, peel and dice your eggs, and set them aside.
In a medium bowl, combine mayo, sour cream, mustard, salt, and pepper. Mix to combine. Add the eggs to the mayo mix and gently stir until combined.
Divide and spread the egg salad evenly between 2 pieces of bread. Top with chopped chives or scallions and top each sandwich with another piece of bread. Serve!