Pour the flour into a large mixing bowl. Whisk in the baking powder and salt. Create a well in the center and break the eggs into it. Mix with a wooden spoon. In a mixing cup or small bowl, whisk together the milk and water. Stirring the entire time, gradually pour in the milk-water mixture, and stir until smooth.
Place the sausage in an even layer in a shallow casserole. Pour the batter over the sausages and bake for 20 minutes. Reduce heat to 375F and bake for another 15-20 minutes. Check frequently to make sure it doesn’t overcook.
Serve immediately, with spicy mustard or horseradish.