(as) happy as a clam in butter sauce
Very joyful and content. Look at your sister out there! She's happy as a clam in butter sauce now that she's back in the starting lineup again. I know I'll be happy as a clam in butter sauce once I get this stupid cast off my leg.
(as) happy as the day is ˈlong/as a ˈclam/as ˈLarry
(informal) very happy: Grandpa’s as happy as a clam helping the children to fly their kites.