Preheat the oven to 180°C.
Lightly butter a 2lb loaf tin (I used this one by Circulon) and line with greaseproof paper (see notes in the post above). Set aside. Stir the dry ingredients (flour and cocoa powder) together in a bowl and set aside.
In a separate bowl, beat the margarine and sugar together until creamy.
Mix in the eggs one at a time, adding 2 tablespoons of the dry ingredients after each egg to stop the mixture from curdling.
Add the remaining dry ingredients and gently fold the mixture together until smooth and fully combined.
Fold in the milk and chopped Creme Eggs.
Spoon the chocolate cake mixture into the loaf tin, smoothing it out the top.
Bake for 55-60 minutes* until risen and a toothpick inserted into the middle comes out free of crumbs. Leave in the baking tin for 15 minutes, then lift the cake out onto a cooling rack and leave to cool completely.