Homemade Chocolate Milk

My daughter is always asking for chocolate milk, and the organic brand is expensive, and the less expensive full of chemicals. I've been using this recipe for homemade chocolate milk:

Fill a lidded bottle like a one quart Rubbermaid drink bottle about 2/3 of the way with milk(20-24 ounces).

Heat milk for about two minutes in the microwave, then add a heaping teaspoon of sifted cocoa powder, and two of sugar(double if you like it strong and sweet). Add about a tablespoon of canola oil, shake well. The heated milk and oil help combine the ingredients, otherwise the chocolate clumps.

Refrigerate and serve cold.

It will still need to be shaken every time you serve it, but the cocoa mixes fairly well.