Note: You will need a slowcooker, and a 4 to 5 cup capacity heatproof bowl that fits inside the crock (with the slowcooker lid on), that has at least 1-2 inches of headroom for oats to expand as they cook. You will also need additional water to make the water bath around the bowl.
Night before: Mix oats, dark brown sugar, molasses, ginger, cinnamon, cloves, nutmeg, salt, golden raisins, half and half and water in heatproof glass bowl that fits inside slowcooker crock.
Center bowl in bottom of crock. Inside the crock -- but outside the bowl full of ingredients -- add water until level with oatmeal mixture in bowl. Cover slowcooker with lid. Turn on low heat. Cook oats for 6 to 8 hours or until you wake up the next morning.
When ready to eat, remove the lid and stir cooked oats well. Spoon into serving bowls, and top with toasted walnuts and candied ginger to taste. Serve with milk if desired.
Leftovers can be kept in the refrigerator in an airtight container for up to three days.