Step 1Heat the oven to 400 degrees.
Step 2In a medium mixing bowl, whisk together the eggs, mayonnaise, mustard, three-fourths teaspoon Old Bay Seasoning, tarragon, onion and celery to make a dressing.
Step 3In a large mixing bowl, toss the bread with half of the dressing, mixing until the dressing is absorbed by the bread and the cubes are slightly broken up. Add additional dressing if the cubes are too dry.
Step 4Gently mix in the crab, being careful not to break up the lump pieces. The mixture should hold its shape when formed into a ball with your hand. If it is too dry, add additional dressing until the mixture comes together. You might not use all of the dressing.
Step 5Divide the mixture and form into 8 crab cakes. Place the cakes on a greased cookie sheet or sheet pan.
Step 6In a small bowl, stir the butter together with the remaining one-half teaspoon Old Bay Seasoning. Top each cake with a small dollop of the seasoned butter.
Step 7Bake the cakes until golden brown, about 10 to 12 minutes. Serve warm.