Up to 3-4 hrs before cooking, mix together the milk, eggs, flour and 2 tsp salt in a food processor or blender until you have a smooth batter. If you don’t have a food processor or blender, whisk the eggs into the flour and salt, then gradually whisk in the milk until smooth. Transfer to a jug, cover and leave at room temperature for at least 15 mins.
Heat oven to 220C/200C fan/gas 7 and brush 12 holes of a muffin tin with the oil. Heat the tin in the oven for 5 mins, then carefully lift out and quickly pour the batter into the holes. Bake in the oven for 5 mins, then reduce oven temperature to 200C/180C fan/ gas 6 and cook for a further 30 mins until puffed, risen and golden.