Medieval people loved to cook with almonds. Many recipes in The Forme of Cury contain them, so it should be no surprise that they also enjoyed almond milk. The rice in this recipe would have come from the other side of the world, so only the richest could afford to make this recipe.
This was basically a medieval rice pudding, and you can find a recipe for it here. Cook the rice, drain it, and place it in a saucepan. Then cover it with almond milk, and simmer for a while. Add honey and sugar, cook until the whole mixture thickens, and voila! Medieval rice pudding.