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

[HardAsSnails]

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

[purpleunicorns]

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

[ClashCityRocker]

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