Baking – Is it okay to put baking powder in Yorkshire Pudding batter

You need to make sure you use the right measurements when translating recipes from the US to the UK as the UK uses imperial measurements which are different from US measurements. There are also differences in cream fat content and egg sizes. Teaspoons and tablespoons are the same, so don't worry about them.

First, pint measurements, as the UK doesn't use cup measurements. The UK pint is 20% bigger than the US pint, so if you are using UK pints to measure you may be getting ratios wrong. Use Milliliters instead when translating. 1 US Cup is 237ml (I round up to 240). If you use UK pints as a measure instead of US you won't have enough baking powder in the ratio. In fact, I find UK baking powder and bicarb a bit weaker than US powders, so I increase those measurements a bit anyway.

What works for me is the first time I make a US recipe in the UK I weigh the dry ingredients and use weights every time I make the recipe after that, I can fine-tune it that way.

US light cream is between 10-30% butter fat, and heavy cream is about 36-40%. UK single cream is between 10-30% fat, whipping cream is about 36%, and double cream is 50% fat. So if you are right that US heavy cream is UK whipping cream, but mixing 2 parts UK double and 1 part single works just as well as many places don't stock whipping cream.

I doubt that your results come from the cream you are using though, the fat contents aren't that different. One thing that could be different is the flour you use. US and UK flours aren't completely the same. For my biscuits in the UK I buy 00 or purpose milled pastry flour, which is finer and better for pastry than the bog standard stuff. If you can't find it pick the flour with the lowest protein content you can find.

Hope this helps, let the forum know your results if you can.

The short answer to your question is YES. The extra acid in the ingredients will hamper the second act of the double acting baking powder. The acids are timed/staged for reaction not the baking soda.

The Magic Baking Powder (happens to be in our kitchen, too) is mostly a single acting formula since monocalcium-phosphate is a low temperature acid (with apparently some double acting properties due to generation intermediate step of dicalcium phosphate; per your link). High temperature acid for second acts typically include sodium aluminium sulfate, sodium aluminum phosphate and sodium acid pyrophosphate.

You can try to counteract that by adding a bit of baking soda, but you run the risk of altering the taste and not having it all neuralized.

If you really want to get pedantic, use a pH meter to measure the acidity of your dough. I suspect tasting the dough might give an indication as well. (bitter alkaline, sour acidic)

Another test might be to mix your acidic ingredients in a bowl with some water and start adding measured baking soda until you see no more reaction (bubbles) and use that as a your basic of neutralizing your dough.

All said and done, I agree with SAJ14SAJ that you'll be just fine going with the existing recipe. There should be enough baking soda left to get something out of your double act. I also heard it from a world-class baker that most recipes can be done with only baking soda, let alone baking powder or double acting ones.