In a small saucepot over medium heat, combine milk, half and half, cocoa powder, and vanilla. Whisk occasionally for 10 minutes, until cocoa powder has dissolved and liquid is not (be sure not to let burn).
While hot chocolate is cooking, dip rim of glass or mug in lime juice, followed by red sprinkles.
When hot chocolate is done cooking, add green food coloring and whisk.
Pour hot chocolate into prepared glass and top with whipped cream, sprinkles, and a cherry.