Mash the banana thoroughly: In a medium mixing bowl, use a fork to mash the banana until it forms a smooth, almost liquid paste with no visible lumps. You should see a creamy, pale-yellow puree with a soft, sticky texture. This takes about a minute of consistent mashing.

Add the dry ingredients: Sift the cocoa powder over the mashed banana to avoid clumps. Add the pinch of salt. The cocoa powder will create a dark, rich cloud on top of the banana. Whisk gently to combine until you have a uniform, dark brown mixture that smells intensely of chocolate.

Incorporate the wet ingredients: Add the Greek yogurt, almond milk, and vanilla extract. Stir with the fork or a small whisk until everything is fully integrated. The mixture should transform from a thick paste into a smooth, glossy mousse-like consistency. It will look like a thick chocolate pudding, with a silky sheen from the yogurt.

Add chia seeds (optional): If using, stir in the chia seeds now. They will add a subtle poppy-seed-like crunch and help thicken the mousse further as it rests.

Chill (or serve immediately): For a mousse that's firmer and colder, transfer the mixture to a small ramekin or glass and place it in the refrigerator for at least 10 minutes. If you're impatient, like I often am, you can eat it straight away. It will be softer and more like a pudding.

Garnish and serve: Just before serving, top with a few fresh raspberries or a dusting of extra cocoa powder. The tartness of the berries cuts through the richness of the chocolate beautifully.