My Grandma used to make these and we loved watching them come out of the oven all poofed up.
Preheat a rectangle glass casserole dish with 1/2 cube of real butter to 425 degrees.
While this is preheating mix the following in your blender...
1 cup milk
1 cup flour
1 tsp salt
When the butter is melted and the oven is preheated carefully pour the batter into the casserole dish and cook for 20 minutes.
Serve with maple syrup, fried apples, powdered sugar, or whatever you can think of.
In England this would be cooked with roast beef drippings and called Yorkshire pudding.
When we're being money or calorie frugal we just use 1 TBSP of butter in the bottom, when we have company we use a whole cube.