Place 1 1/2 cups of the breadcrumbs on a flat plate.
In a bowl, mix shrimp, mayonnaise, eggs, scallions, garlic paste, mustard, pepper, salt, and the remaining 1/2 cup breadcrumbs until combined. Measure 1/2 cup of mixture into a shrimp cake (mixture will be wet). Turn out cake onto breadcrumbs, coat completely. Make 7 more cakes and transfer to a baking sheet lined with wax paper, flatten cakes slightly, to a 3 1/2 inch circumference. Refrigerate 1 hour.
IN a large non stick skillet, heat 2 tbsp of the oil over medium heat. Add 4 cakes and cook, about 4 minutes per side, until crisp and browned. Transfer to a plate, loosely cover with foil and keep warm in a 200 degree oven. Repeat.
Lemony Tartar Sauce: combine all ingredients, stirring to blend.