I had the same problem, I used to make great yorkshires and then for some reason couldnt, I now use the exact amount of ingredients as the above recipe (1/2 pint milk, 3 eggs, 4oz flour & pinch salt) only it was a mike robinson saturday kitchen recipe. Basically I put all the ingredients together quite slapdash in a tupperware tub, put the lid on (securely) and shake hard. Then put this in the fridge. I put veg oil in 4 hole yorkshire pudding tins, and heat on MAX (fan assisted electric oven) for about 5/10mins, until slight smoke coming off, transfer the mixture into a jug and pour into the tins, should sizzle and start to bake straight away. Close the door and cook for 20 mins. I cook 12 and even though the last tin doesn't sizzle as much as the others, they all come out evenly. And I have opened the door at times during cooking although I try not to. It's something to do with the amount of eggs I think.