Preheat oven to 350ºF.   In a large bowl, combine crackers, drained oysters, melted butter and black pepper to taste. Stir gently till well mixed. Add evaporated milk to reserved oyster liquid to make 2 cups. Pour into cracker-oyster mixture, stir gently to mix well. Spoon mixture into greased casserole dish ( I use my deep "French White" Pyrex casserole dish). Pour enough milk over mixture to make it "soupy". Milk should be to top of mixture. Bake at 350ºF.  for 30-40 minutes until "puffed" and lightly browned.