For The Cake
Place rack in the center of the oven and preheat the oven to 350°F. Brush Cake Magic onto the inside of a 10-cup Bundt cake pan. (Alternatively, butter and flour the inside of the cake pan.)
In a medium saucepan, combine butter, cocoa powder, salt, and water. Melt over medium heat, stirring to combine. Remove from heat and set aside.
In a large mixing bowl, whisk together flour, sugar, and baking soda. Gradually pour in the chocolate mixture, whisking constantly with your opposite hand, until the mixture is smooth. Add eggs, one at a time, whisking until combined after each addition. Whisk in the sour cream and vanilla extract until smooth.
Chop the head of black garlic in half, then remove cloves from the skin and place in a small mixing bowl. Mash cloves into a paste with the back of a spoon. Whisk the black garlic paste into the cake batter until smooth.
Pour the batter into your prepared Bundt cake pan and bake until a toothpick or cake tester inserted in the cake comes out clean, 40-45 minutes. Place pan on a wire rack to cool for 15 minutes, then invert the cake onto the wire rack and let it cool completely.