1 Tear Up The Bread And Pulse In A Food Processor To Make Fine, Soft Crumbs (About 4 Cups). Transfer The Bread Crumbs To A Shallow Pan And Mix In 1/2 Cup Of The Parsley. 2 In A Food Processor, Combine The Egg Yolk, Lemon Juice, Worcestershire Sauce, Tabasco Sauce, Mustard, Paprika, Thyme, Celery Seeds, And Black Pepper. Pulse To Combine. With The Motor Running, Add The Oil Through The Feed Tube In A Slow, Steady Stream Until The Mixture Emulsifies And Forms A Mayonnaise-Type Sauce. Transfer Sauce To A Bowl. 3 In A Large Bowl, Combine The Onion And Bell Pepper With The Remaining 1/4 Cup Of Parsley. Add The Mayonnaise-Type Sauce And Crabmeat And Mix Lightly. Using A Rubber Spatula, Fold In 1 Cup Of The Bread Crumb Mixture. Do Not Overwork The Mixture. Gently Form 6 Cakes And Flatten Them Into Patties About 1/2 Inch Thick. Dredge The Patties Lightly In The Remaining Bread Crumb Mixture. Cover The Crab Cakes With Plastic Wrap And Refrigerate For An Hour Or Longer. 4 Heat A Large Non-Stick Skillet On Medium Heat And Add About 2 Tbsp Of Butter To The Pan. Working In Batches, Fry Crab Cakes Gently 4 To 5 Minutes On Each Side, Until They Are Golden Brown And Heated Through. Add More Butter To The Pan If Necessary. 5 To Prepare The Horseradish Mayo, Combine All Ingredients In A Small Bowl And Mix Well. Taste And Adjust Seasoning. Cover And Refrigerate.