Cocoa powder doesn't dissolve in cold milk though, does it??
It goes very well in hot milk though. This is what you want to start the day - chocolate porridge.
I thought that was a bowl of minced beef 
Semi-skimmed milk with any flavour milkshake powder added will work. As would making a smoothie with milk and fruit. You want around 50-75g of carbohydrates in the 30-45 minutes post-exercise (ideally), and adding protein increases muscle glycogen re-synthesis and also stimulates muscle repair and adaptations. A ratio of around 4 to 1 carbs to protein (so 12-18g protein to go along with the 50-75g of carbs).
Having it in fluid form also helps to rehydrate - if you can manage solids/prefer them, then just eat a carb/protein snack, but make sure you have a drink along with it. And ideally have it as soon as you can after training/competition for optimum benefit 