Preheat the oven to 325 F degrees. A grease casserole dish with extra butter. Spread the cheese in the bottom of the casserole dish. Cut the butter into small chunks and dot over the cheese.
Combine the milk and wine. Pour half the mixture over the cheese.
Beat together the eggs with salt, pepper, and dry mustard. The eggs should be fully combined and slightly frothy.
Pour the remaining milk/wine mixture over eggs.
Bake until the eggs are slightly puffed and just set, approximately 35 to 40 minutes. Beginning checking at 30 minutes, then every few minutes until the center is just slightly jiggly. Rest for 5 minutes before cutting into squares, garnish with chives.
A 9x13 or larger casserole dish is recommended for this recipe. In order to cook without getting crusty, the casserole needs to be on the thinner side.
Bake on the bottom rack to prevent the top from over-browning.
Layering the ingredients is important in this casserole dish.