Oyster sauce is a thick brown sauce made from oysters, salt, water and starch. It gives this recipe a rich flavor and can be found in the ethnic section of your grocery store or at Asian food stores.
Cook the noodles the night before and place them in a resealable plastic bag with a little oil. Store in the refrigerator until it’s time to prepare the meal. Add the noodles after cooking the spinach for about 1 minute; continue cooking until heated through.