George’s Marvelous Medicine by Roald Dahl

George is alone in the house with grandma. The most horrid grizzly old grunion of a grandma ever. She needs something stronger than her usual medicine to cure her grouchiness. A special grandma medicine, a remedy for everything. And George knows just what to put in it! Graeme is in for the surprise of her life, and so is George when he sees the result of his mixture!