In a large bowl, combine mayonnaise, Dijon mustard, egg, lemon juice, salt, and pepper.
Stir everything until well mixed.
Gently fold in the crabmeat and chives into the mixture.
Be careful not to break apart the crab pieces.
Add panko breadcrumbs and use your hands to mix everything.
The mixture should bind together easily.
Shape the mixture into cakes, about 1/2 inch thick.
Refrigerate them for at least 30 minutes.
In a large skillet, heat the vegetable oil and butter over medium heat.