Place all ingredients except the nuts in a slow cooker and stir to combine. Set on low, and allow to cook overnight. Stir well before serving, adding more milk as needed. Top with a sprinkling of walnuts (about 2 tablespoons per serving). Store leftovers, covered, in the refrigerator or freezer.

Stovetop method: Reduce liquids to 2½ cups each of milk and water. Combine everything except the nuts in a large pot and heat over medium-high heat until just barely boiling. Immediately lower heat to low, cover, and cook for 30-45 minutes, stirring frequently, until the quinoa is cooked and creamy. Add nuts and stir to combine. Serve warm or cold.