Yorkshire puddings rise because of the eggs in them. This means that the mixture for you Yorkshire puddings needs heat to rise So if your oven is not hot enough, they won't rise as much as you want. So here are some tips:
-make sure your oven is hot before putting your puddings in
-Don't open the oven while cooking your puddings
-I always pre heat the muffin trays before I use them.
So you put your mixture in a hot muffin tray (or something els you use), put the hot muffin tray in a hot oven, and don't open the oven anymore before the cooking time is over. So I won't use baking powder, I first try it by making sure the heat is there.
Note that of course every oven is different and so you might need a couple of time before have the right temperature. Also I recommend this site for more information about Yorkshire puds: http://www.hub-uk.com/tallyrecip03/recipe0124.htm
There are two reasons (that have also been discussed in many other questions)
Baking powder isn't just sodium bicarbonate + acid. It often also contains aluminum compounds that release gas when they are heated. That means they will make bubbles not just when the batter is mixed but also when it is baking.
Baking powder is ph neutral while baking soda is basic. Recipes will often include mostly baking powder with some soda to neutralize acidic ingredients.
See also:
What is the difference between baking soda and baking powder?
Best Answer
The baking powder undergoes a chemical reaction which produces small gas bubbles in the batter. The bubbles break up the batter coating (sort of like the geometry inside a sponge) so you wind up with a mass of little holes each surrounded by a thin layer of bready material, and it all fries up airy, light and crispy; instead of one thick, dense, hard shell of cooked paste around your cauliflower bits.