This is the recipe I use when I make Prime Rib. I never go without Yorkshire pudding when I make Prime Rib. This uses the rendered juices from the roast. Perfect for soaking up the great Au Jus that the roast renders! This method is a do ahead method for the batter. Then you can make them when the roast is resting after coming out of the oven.
EARLY ON THE DAY YOU ARE MAKING PRIME RIB FOR DINNER:
Whisk the 2 eggs with 1/2 cup of the milk,set aside.
In a large bowl, whisk the flour and salt together. Add the egg and milk mixture and whisk vigorously until there are absolutely no lumps left in the batter. (a Kitchen Aid is great for this!)
Cover the batter with plastic wrap, and keep it at room temperature all day until you are ready to use it (at least 5 hours)
WHEN YOU ARE READY AND THE PRIME RIB IS RESTING:
Heat oven to 425 degrees. (the oven will already be heated if you are just taking out the Prime Rib)
Place a standard 12 muffin sized pan in the hot oven and heat it up until it is very,very hot.
Measure out 1 teaspoon of the pan drippings into each muffin cup and place back in the oven. Leave it in there until the fat is literally smoking hot. I do mean smoking. Takes about 5 minutes,but just look for the smoke.
As the fat is heating, whisk in the remaining 1/2 cup of cold milk into the batter that has been sitting out all day. The milk must be cold,straight from the fridge. (when you make the batter in the morning, put a note on it to remind you to add the additional 1/2 cup of cold milk so you dont forget....I have forgotten in the past)
When the drippings are smoking and hot, take the pan out and working as quickly as you can, pour the batter evenly into the muffin cups. You will see as the batter hits the hot drippings, it will bubble and sizzle. If it doesnt, it wasnt hot enough. If it wasnt hot enough, you cant un-do it, it will still taste good, but you wont get the rise unless the drippings are smoking hot.
Immediately return pan to oven and bake for 20-25 minutes. Do NOT open the oven door for the first 20 minutes of baking. It is done when the pudding is a dark golden brown and dry to the touch and has risen very high.
Serve immediately along with the Prime rib and Au Jus.
You can easily double or triple this recipe (or half it for that matter) just as long as you remember to add the remaining cold milk later.