Biscoff cookie butter (also called Biscoff spread) is a spreadable paste with a texture similar to thick peanut butter. The number one ingredient in the cookie butter is, of course, Biscoff cookies! Biscoff cookies have a deep caramel flavor with a touch of warm spice. This is why I developed this Biscoff mug cake with brown sugar and cinnamon, to complement the flavors already present in the cookie butter. I have found Biscoff cookie butter in my regular grocery store, in the same aisle as peanut butter (here in the US). You can also find Biscoff cookie butter on Amazon. Try this combo pack, with crunchy and smooth cookie butter, plus a pack of Biscoff cookies! (affiliate link). (Although Biscoff cookie butter, made by the company Lotus, is arguably the most well-known, other companies also make cookie butter, such as Trader Joe's. Feel free to use any brand of cookie butter for this mug cake recipe! )