Arrange frozen fries or tots on parchment-lined baking sheet and cook 25 minutes to golden.
For the sauce: In a bowl combine yogurt, mustard, zest and juice of lemon, capers and relish or chopped cornichons. Chop and add herbs and grate in a clove of garlic or chop and add, then stir and season with salt and pepper.
For the fishwiches: In a shallow bowl or pan combine flour, cornstarch, Old Bay, granulated garlic, salt and pepper. Dress the fish with juice of a lemon.
In a shallow dish or pan whisk together the eggs and milk or half-and-half.
Cut bread into 1/2-inch slices and light- to medium-toast the slices.
Heat the oil, 3 turns of the pan, in a large skillet over medium to medium-high heat, add butter. When butter foams, coat fish in flour, then shake off excess; dip in eggs and cook in pan to deeply golden on each side, 3 to 4 minutes. Drain on wire rack lined baking sheet. Cut remaining lemon into wedges.
Serve fish on toast points open-faced or on whole slices as sandwiches piled up with lettuce and a lot of sauce, with lemon wedges on the side. Serve fries or tots alongside with vinegar to pass.