First prepare the batter:
Using yolk and white of one egg, beat each separately and thoroughly. Then combine both, adding enough superfine powdered sugar to stiffen. Add to this one pinch of baking soda and the 1/4 ounce of light rum to preserve the batter. Then add a little more sugar to stiffen.
To serve, use hot mug, using one T of above batter, dissolved in 3 T hot milk. Add rum. Then fill mug with hot milk within 1/4 inch of top of the mug and stir. Then top with brandy and sprinkle a little nutmeg on top.
The secret of a Tom-and-Jerry is to have a stiff batter and a warm mug.