Beat together the butter, milk, and eggs, then add to dry ingredients and mix well
Butter the mold (the bowl you will be cooking the pudding in) then place the pudding mixture into the mold. Some people also line the mold with parchment paper to make it easier to get the pudding out of the mold after it is cooked.
After wrapping the mold in buttered grease paper and aluminum foil (see BBC video below) place mold in steamer pan to steam for two or three hours til done
An English pudding may be steamed in
A. A steamer pan (similar to a double boiler with holes in the bottom of the top pan)
B. A Slow cooker
C. A large stock pot on the stove
It can also be done in a slow cooker: After the pudding is wrapped (see BBC video above) place the pudding mold into the slow cooker. Pour in sufficient water to come 1/2 way up the sides of the pudding bowl. Cover and cook on HIGH for 5-7 hours. (You may need to scrunch up a bit of aluminum foil, or use an inverted saucer to lift the mold off the bottom of the crock pot.)
No matter the method, be sure to also keep a kettle of hot water on the stove, so you can top up the hot water in the steamer pan every so often. You don't want the steamer pan to go dry, it must have water and steam in it continually to finish steaming the pudding and since steam evaporates, the water level will need to be replenished. Just keep checking it every so often. You also do not want the hot water to bubble into the mold, that would ruin the pudding, so that is why the water level must be kept at half way up the bowl (mold) and the heat must keep the water steaming but not at a rolling boil.