Step 1: Prepare Dry Ingredients

In a large mixing bowl, combine 1.5 cups of self-raising flour (if using plain flour, add 1.5 teaspoons of baking powder), 1 cup of caster sugar, 0.5 cup of good quality unsweetened cocoa powder, and 100g of roughly chopped semi-sweet dark chocolate. Mix these dry ingredients together until well combined. Set aside.

Step 2: Prepare Wet Ingredients

In a separate mixing jug, add 1 cup of buttermilk, 80g of melted butter, and 1 egg. Whisk these wet ingredients together until they are combined. It's perfectly fine if the mixture looks a little lumpy or curdled.

Step 3: Combine Wet and Dry Ingredients

Create a small well in the center of your dry ingredients. Pour the wet ingredients into this well. Gently and carefully mix the ingredients together using a wooden spoon until they are just combined and moistened. Do not overmix; a slightly lumpy batter is ideal for muffins.

Step 4: Fill Muffin Pan

Divide the muffin batter evenly among the 12 holes of a muffin pan that has been lined with paper cases.

Step 5: Add Chocolate Topping

Take the remaining 100g of roughly chopped semi-sweet dark chocolate and sprinkle it on top of each muffin. Gently press the chocolate pieces down slightly so they adhere to the batter.

Step 6: Bake Muffins

Place the muffin pan into a preheated oven at 200°C (400°F). Bake for approximately 20 minutes, or until a skewer inserted into the center of a muffin comes out clean.

Step 7: Cool and Serve

Once baked, remove the muffins from the oven and leave them in the muffin pan for at least 10 minutes to cool down and finish cooking on the inside. After cooling, they are ready to be enjoyed.

Step 8: Freezing Instructions

If you have leftover muffins or wish to prepare them in advance, allow them to cool completely. Then, place them in zip-lock bags and store them in the freezer for up to 12 months. They can be defrosted at room temperature or warmed in the microwave before serving.

• Use good quality unsweetened cocoa powder (Dutch cocoa if possible) for a more intense flavor and to avoid extra sugar.

• If you don't have buttermilk, you can make a substitute by adding 1 tablespoon of lemon juice or white vinegar to 1 cup of full cream milk. Stir and let it sit for 5 minutes.

• Do not overmix the muffin batter; mix gently until just combined and moistened. A lumpy batter is perfectly fine and will result in tender muffins.

• After baking, leave the muffins in the pan for at least 10 minutes to cool and finish cooking on the inside.

• These muffins are fully freezable for up to 12 months. Allow them to cool completely, then store in zip-lock bags. Defrost at room temperature or warm in the microwave before serving.

• For an extra decadent treat, add a swirl of chocolate frosting on top after the muffins have cooled.