Preheat the oven to 180°C (160°C fan/Gas Mark 4).

Line a 6-hole muffin tin with muffin cases.

Place the butter and 75g milk chocolate in a heatproof bowl over a pan of simmering water until melted, ensuring the bowl does not touch the water.

Remove the bowl from the heat and stir in the granulated sugar.

Gradually beat in the eggs using a wooden spoon.

Fold in the self-raising flour until smoothly combined.

Spoon the mixture into the muffin cases, filling each halfway.

To make the ganache, place the remaining chocolate, double cream, and instant coffee granules in a heatproof bowl over simmering water, ensuring the bowl does not touch the water.

Once the chocolate has melted, remove from the heat, stir thoroughly, and allow to cool slightly.

Spoon a teaspoon of the ganache into each muffin case, then top with the remaining muffin mixture.

Bake for 20-25 minutes, or until the muffins are springy to the touch.

Transfer the muffins to a wire rack.

While the muffins are hot, top each with the remaining ganache, smoothing it with a round-bladed knife.

Serve warm or cold.

Store the muffins in the fridge for up to 2 days.