Kidney fat from mutton or cow that is of a creamy white texture, not discolored. All connective tissue removed. Mince up very fine. Heat up very slow in a caste iron pot, set near fire or on low heat so as not to cook but to warm up and separate leftover connective tissue. Should take several hours of heating. Alternative is in slow cooker on medium heat overnight. Sieve the fat to separate out connective tissue (grapes). Pour into containers so that they set and solidify. Wrap in paper or linen to preserve for later.