The Case of the Missing Deed by Ellen Schwartz
Their grandmother is so sick over this invasion of the island that she can barely get out of bed each day. She gets even weaker when they can not get her to eat a thing. The cousins are determined to find the deed, but first they need to help their grandmother gain some strength and help them. All the cousins remember that their grandmother loved to cook for them when ever they came over to the cottage. This gives them an idea to cook for her. They go looking in her recipe box and try different recipes. They start to find grandpas writing on some of the recipes but they have no idea what he is trying to say. Could these mysterious writings be clues as to where the deed might be? They search through more recipes and find more sayings that have them really confused.
Sabastien, Genevieve, Claire, Olivia and Alex all try desperately to help grandma keep her home., but will they be successful?
For a quick read and several good recipies try reading "The Case of the Missing Deed".