Drain sauerkraut in a colander. Then, place in the center of a clean, dry tea towel. Pull the sides of the towel up & twist it, squeezing as much liquid from it as possible from the sauerkraut. Or, grab fistfuls of the kraut & squeeze it to remove the liquid. Leave to drain further in the colander.
Split each brat down the center & peel off casing, dropping the insides into a large bowl. Add sauerkraut, 1/4 cup of breadcrumbs, onion, parsley, mustard, garlic, cheese, salt & pepper. Stir until all ingredients are thoroughly combined – using your hands works best for this - it’s important to ensure the mixture is thoroughly combined.
Cover a baking sheet with parchment or waxed paper. Roll mixture into 2 tablespoon balls.
Whisk eggs & milk in a medium, shallow dish until combined. Place flour in another shallow dish; season generously with salt & pepper. Add remaining breadcrumbs to a third dish.
Gently toss each ball lightly into flour then dip into egg mixture, draining away excess egg. Roll in breadcrumbs & place back on the baking sheet.
Heat oil in a wok or large saucepan until it reaches 350F. Cook the balls in 4 to 5 batches for 6 minutes or until a deep golden brown & cooked through. Drain on paper towel & keep warm in the oven until ready to serve. Makes about 24. Serve with mustard & cornichons, if desired.