To prepare crepe batter (do ahead and let rest)

Cup of Yum
1. Put all of the crepe ingredients (milk, egg, flour, melted butter and salt) in a blender and blend together until smooth. Alternatively mix with a hand blender. Set aside for a good 30 minutes or more, if possible, or at least while you prepare the filling.

For apple filling

1. Peel and core the apple and cut into small slices or a relatively small dice. Add the lemon juice to the bowl, toss gently, then add the cinnamon and brown sugar. Mix everything together so the apples are evenly coated.
2. Warm the butter over a medium-low heat in a medium skillet/frying pan and add the apples. Stir to coat the apples in the butter and spread into an even layer. Cook for around 6 - 8 minutes, stirring now and then, until the apples are gently soft and the liquid has reduced to a thicker more caramel-like consistency. Set aside.

To cook crepes

1. Warm a crepe pan over a medium heat and brush lightly with oil or use a little butter (if needed - may not if it's a seasoned non-stick). Using a small scoop or measure, take approximately ¼ cup (60ml) of the mixture at a time, or more for a larger pan, and swirl on the pan to create a thin relatively even layer. The best way is to hold it as you pour on in the middle, and rotate the pan to circle it round. 
2. Leave the crepe on the heat until the surface is dry and the edges start to gently brown and curl up. Flip over and cook a minute more on the other side. Remove from pan or flip over again, if needed, and add a spoonful of the apple filling, roll up the crepe and serve. Alternatively, you can place the crepes in a stack wrapped in a clean cloth while you cook the rest then add filling to all of them at the end. You can also add a little cream or ice cream to serve, or dust with powdered sugar.