Marbled chocolate cupcakes

Marbled cupcake recipe is from  "muffins & bakes" book. 

Ingredients:

• 175 grams soft margarine
• 175 grams caster sugar
• 3 eggs
• 175 grams self- raising flour
• 2 tbsp milk
• 55 grams plain chocolate melted

Method:

1. Put 21 paper baking cases in a muffin pan.
2. Put the margarine, sugar, eggs, flour and milk in a large bowl and, using an electric hand whisk, beat together until until just smooth.
3. Divide the mixture between 2 bowls.
4. Add the melted chocolate to one bowl and stir together until well mixed.
5. Using a teaspoon, and alternating the chocolate mixture with the plain mixture, put four half-teaspoons into each paper case.
6. Bake the cupcakes in a preheated oven 180C for 20 minutes or until well risen and springy to the touch.
7. Transfer to a wire rack to cool.