In a medium-sized bowl, combine the dry ingredients (flour, semolina, sugar, and salt) and set aside.
In a separate bowl, whisk together the wet ingredients (water, milk, and vanilla extract). Then add the dry ingredients to the wet ingredients and give everything a good whisk until well combined. A few lumps in the mixture is ok.
Cover with a towel, and allow the batter to rest in a warm place for 20-30 minutes.
Heat a non-stick pan or a griddle over medium-high heat, then pour the batter from a jug or using a spoon to create little circles (for small Atayef pour 1 tablespoon of batter, for medium-sized ones do 2 tablespoons, and ¼ cup for the large ones).
As the Atayef cook, lots of bubbles will appear. Keep cooking (do not flip) until these bubbles dry out (about 2 minutes). If no bubbles are appearing, you might need to add a little bit of more water as your batter is probably too thick.
When the bubbles dry out completely and the surface is no longer shiny, it means that the atayef are done. Remove immediately, and repeat the process until you finish up the batter.
Transfer the atayef to a tea towel and cover very well so that they don't dry out (otherwise they will start breaking when you try to fold/seal them).