In a 1 1/2- or 2-quart slow cooker or a 1 1/2-quart casserole combine almond milk, the water, millet, quinoa, oats, and salt.
If using the 1 1/2-quart casserole, place casserole inside a 5- to 6-quart slow cooker and add enough water to cooker to reach halfway up sides of casserole. Cover slow cooker and cook on low-heat setting for 6 to 8 hours.
Stir the 2 tablespoons honey and the cardamom into hot cereal. Top individual servings with mango, blackberries, and, if desired, almonds. Drizzle with additional honey and/or sprinkle with turbinado sugar.