Do not use butter for frying. High temp oils such as Grape seed has a higher smoke point above Vegetable, Canola. Peanut oils are a high temp too but can leave a taste in you fried foods. Key to frying anything is to dry your food with paper towels. In other words take the fish and rinse it off well lay out plenty of paper towels and lay the fish into it take more paper towels and lightly press on flesh to dry. repeat if you get moisture on the towels.
You really will not dry 100% but when the fish become tacky to the touch you will know by feel then bread the fish normally. Flour Egg wash coatings. Don't over flour the fish either just a light dusting is needed. When your fish is placed in the hot oil it really shouldn't splatter much if at all that is the key to a flakey fish. WHat you are doing if it is not flaky is basically poaching or steaming the fish making the flesh somewhat mushy. Frying is a process of sealing the flesh trapping in some moisture and then adding heat to cook. Same as pan siring a steak high heat flip once. Try this method with your fish it works. By the way get a good thermometer too for the oil so you don't undercook the fish and burn the crust a proper temp will give you the best results. The thicker the fish lower the temps while cooking so the middle of the fish isn't raw.
