Yorkshire puddings deflating!

[Candycakes]

My Yorkshire puddings always rise really high and look impressive for about 10 seconds after taking them out the oven then they deflate.

What am I doing wrong?

Can anyone give me the best recipe please?

Currently I use, 100ml milk, 2 eggs & 70gr plain flour

If they deflate you haven't cooked them long enough.

Leave them in the oven a bit longer, even if you need to turn the temperature down, and whatever you do don't open the oven door until they're ready

Yup leave them in the oven longer turning the temp down if neccessary