The Recursive Recipe

A famous chef encoded their secret recipe using a peculiar method. They started with the ingredient list, converted each letter to its position in the alphabet (a=1, b=2, etc.), then applied a recursive transformation: each number becomes the sum of its digits, repeated until a single digit remains. Finally, they concatenated all single digits together. The encoded recipe is: 91943494319559594. The recipe contains exactly 5 ingredients from this list: [butter, cream, eggs, flour, salt, sugar, yeast]. To verify you decoded correctly, the chef hid a flag in the ingredients. Take the first letter of each decoded ingredient in order, combine them, and wrap in the flag format. For example, if you decoded 'butter' and 'salt', the flag would be hc{bs}.