A chocolate malt ball, in powder form. Why DIY Ovaltine? It's easy! And you can adjust the levels of sweetness, maltiness, chocolatey-ness, etc. to your preferences. In fact, you can adjust the levels of everything to your preferences—which means that if you want to use a non-dairy milk powder, you can. (And you can make it in bulk.)
There are two approaches to this: If bulk Ovaltine isn't something you're interested in, the first recipe is for you (but you will cede your ability to control the exact amount of sugar, since most malted milk mixes do have added sugar). If bulk Ovaltine does sound up your alley, or you have the pantry space to accommodate cartons of milk and malt powders, follow the second recipe and sweeten to taste. —Caroline Lange
Add-ins (like espresso powder, cinnamon, or cardamom) to taste
Regardless of the variant you choose (bulk or non-bulk), combine all ingredients in a bowl. Whisk them together, then sift them over another bowl (either with a sifter or through a fine-mesh strainer). Store the powder in a jar with a tight-fitting lid.
To serve, combine 2 tablespoons with hot or cold milk and stir until combined. It will resist mixing completely with cold milk and may settle on top. If this bothers you, shake the milk and the powder together in a jar with a lid, and pour back into your glass.