In a medium saucepan, while stirring, heat the butter, sugar, and half and half on low heat until melted and well combined.
Stir in the marshmallows, turn the heat up to medium, and while continuing to stir bring to a boil and cook for 5 minutes or until all the marshmallows are melted, and the mixture is thick and in strands. When you pull the spoon up, it should be in thick strands like taffy. It's very important that the mixture gets hot enough or it might not set. (If it's super humid, however, it may never set.)
Turn off the heat and stir in the chocolate chips, vanilla, cinnamon, cayenne, salt, and pecans until well combined. The chocolate chips should melt immediately and the mixture will be thick.
Spread the fudge evenly into the prepared pan and refrigerate covered for 2 hours or until set. To serve, lift the fudge out of the pan and cut into 16 (or 32, if you prefer) pieces.
Mexican chocolate fudge | www.homesicktexan.com