Preheat oven to 350 degrees F. Lightly coat a mini bundt pan with nonstick spray.
In a large bowl, combine flour, sugar and baking soda; set aside.
In a small saucepan, combine butter, cocoa powder, salt and 1 cup water over medium heat. Cook, stirring, until melted and combined, about 2-3 minutes. Pour mixture over dry ingredients and stir using a rubber spatula just until moist. Beat in eggs, one at a time, until well combined. Beat in sour cream and vanilla until well combined.
Scoop the batter evenly into the bundt pan. Place into oven and bake for 20-25 minutes, or until a tester inserted in the center comes out clean.
Remove from oven and let cool for 15 minutes before inverting the cake onto a wire rack.
To make the glaze, combine heavy cream and sugar in a small saucepan over medium heat. Remove from heat. Stir in chocolate and corn syrup. Whisk until smooth. Drizzle the glaze evenly over the top of the cakes, allowing to drip down the sides.