Preheat the oven to 350°F. Grease 4 cavities of a mini Bundt pan well and dust them with cocoa powder.

In a medium bowl, whisk together the flour, cocoa powder, baking soda and salt.

In another bowl, whisk the sugar, melted butter, egg, milk and vanilla until smooth.

Stir the wet ingredients into the dry until just combined.

Gently fold in the raspberries.

Divide the batter among the cavities, filling each about two-thirds full.

Bake for 18–20 minutes, until a toothpick comes out with a few moist crumbs. Cool in the pan for 10 minutes, then turn out onto a rack.