You guys make dutch babies in US, don't you? Similar thing, only Yorkshire pudding batter doesn't have sugar in it.
Originally Yorkshire pudding was cooked in one big tray under the spit roast to catch all the drippings and served before the main meal so you'd fill up with bread and eat less meat. Nowadays it's usually individual puddings, cooked on a special tray with wide shallow holes or on a regular muffin tray. You want the tray piping hot before pouring in the batter so get the oiled tray in the oven warming up at least 15 minutes before. Use caution, don't burn yourself. You can use oil or animal fat of your choice. 350-390°F, if I converted right. (180-200°C). When you fill the divets, the batter should sizzle and when returned to the oven, should start rising high from the edges. Try not to open the oven at least 15 min in the beginning as it can sink the yorkies. Check after 25 min or so, the yorkies should look like golden cups, the hole Iin the middle set and yellow, the edges and the bottom browned. Depending on the temperature and the oven, it can take up to 45 min.
As for the batter, ignore all the recipes and follow a simple formula: even amounts of egg, milk and flour, pinch of salt. Roughly half an egg per nase so mix with 2 eggs should serve 4. Measure with a small cup or a measuring cup and tip it all in the bowl. Two schools about it: mix just lumps out or beat the hell out of it. I go to town with a stick blender until the mix is frothy.
Serve it with something with a lot of gravy. Roasted joint (beef, ham, chicken) and veggies is the most common way. Also good for snacking, rip pieces and dip in gravy, delish!
Sorry, got a bit carried away but I've cooked yorkies for living for over a decade now so...