Preheat your oven to 200° C / 180° Fan /Gas 6 /400° F with a shelf just above the middle.

Put a paper case into each hole of a 12-hole deep muffin tin.

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

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

Add the flour mixture to the beaten wet ingredients then start folding in with a silicone spoon or similar. When most of the flour has been incorporated, fold in the chocolate pieces until they're evenly distributed, but try not to over-mix.

Divide the mixture between the muffin cases and sprinkle the top of each one with a little demerara sugar before putting in the oven.

Bake until the muffins are risen, golden, and a cocktail stick or skewer comes out clean (approx. 17 minutes).

Tip: if the tops are browning too quickly before the centre of the muffins are cooked, turn the oven down a little.

Transfer to a cooling rack until cold.

Melt the chocolate in a microwave using 10 - 20 second bursts, stirring after each burst.

Drizzle over the muffins: either off the end of a spoon or from a small piping bag.

To serve warm, heat briefly in a microwave.

Store in an airtight container (in the fridge if the weather is warm), eat within 2 days or freeze.