I discover Aleks making a potion on the counter, a la Severus Snape.
Our Half-Blood Prince stole expensive organic ingredients from our spice cabinet and dumped them in a bowl, creating a noxious combination of unpleasant flavors.
The bubbling actually comes from the interaction between a packet of Emergen-C (lemon-lime, which when combined with the cocoa powder was delish! retch!) and a bit of soapy water. So it fizzed wonderfully, like a truly toxic concoction. I'm not sure precisely what this was intended to do, but we stored it in a test tube for a week.