According to Official Guinness Records,
The largest muffin weighed 146.65 kg (323 lb) and was baked by Schär and NIP food in Milan, Italy, on 16 october 2015.For this record a muffin is a type of bread, usually sweet, which is baked in small, circular portions that rise when baked. The ingredients used to make the muffin include: gluten free flour, butter, sugar and baking powder.
For a complete list of 2015 records, please visit 2015 Guinness Records in Italy.