1. Preheat the oven to 200C/180C fan/Gas 6. Line muffin trays with paper cases (recipe should make 12-14 depending on the size of your muffin cases).

2. Sift together the flour, cocoa powder, baking powder & salt then set aside.

3. Take a large bowl and put in the eggs, yogurt, sugar, vanilla extract and melted butter. Beat together until well combined.

4. Tip the flour, cocoa powder baking powder and salt mixture into the large bowl with the beaten wet ingredients.

5. Using a rubber or plastic spoon, fold in the flour mixture and the chocolate chunks. Do not over-mix: fold until the ingredients are just combined.
   

6. Divide the mixture between the muffin cases.
   

7. Bake until the muffins are risen and a skewer comes out clean (approx 17 minutes).

   NOTE if the tops are browning too quickly before the centre of the muffins are cooked, turn the oven down to and continuing cooking.

8. Transfer the muffins to a wire rack and leave until they're completely cold before adding the melted chocolate topping.
   

For the chocolate topping

1. Melt the chocolate in the microwave, stirring after each 10 seconds (it should take approx 30-50 seconds in total).

2. Put the melted chocolate in a piping bag or a freezer bag with a corner snipped off and drizzle over the tops of the muffins. Alternatively, just drizzle off the end of a spoon.
   

3. If adding the optional topping, sprinkle the seeds over while the chocolate drizzle is still runny. Set the muffins aside until the drizzle is firm.