Preheat the oven to 180°C fan.
Mash the banana, then whisk in the Greek yoghurt, milk and vanilla.
Mix the oats, chocolate protein, cocoa, flaxseed, chia and baking powder in a separate bowl, then stir into the wet mix. If it looks thick, loosen with a splash more milk — protein powder firms up as it bakes, so you want the batter loose and pourable.
Fold most of the raspberries through (save a few for the top). Pour into a glass dish. Push the squares of dark chocolate down into the middle, spacing them so each portion gets a molten pocket.
Bake for atleast 25 mins, until just set around the edges but still soft in the centre. Don't overbake, or the protein powder can dry it out.
Serve warm, straight away, so the chocolate's still molten. Cut in, top with a dollop of Greek yoghurt and the extra raspberries.
