Preheat the oven to 350°F (175°C). Grease and flour a 10-inch bundt pan thoroughly.
In a medium bowl, sift together the all-purpose flour, baking powder, baking soda, salt, and unsweetened cocoa powder. Set aside.
In a small bowl, combine the boiling water and semi-sweet chocolate chips. Stir until the chocolate is completely melted and smooth. Set aside to cool slightly.
In a large mixing bowl, cream the softened unsalted butter and granulated sugar together using an electric mixer on medium speed until light and fluffy, about 3-4 minutes.
Add the eggs one at a time, beating well after each addition. Mix in the vanilla extract.
Alternately add the dry ingredients and the milk to the butter mixture, beginning and ending with the dry ingredients. Mix each addition just until combined.
Stir in the sour cream and the melted chocolate mixture until the batter is smooth and uniform.
Pour the batter evenly into the prepared bundt pan and smooth the top with a spatula.
Bake in the preheated oven for 50 minutes, or until a toothpick inserted into the center comes out clean.
Remove the cake from the oven and allow it to cool in the pan for 15 minutes.
Invert the cake onto a wire rack and let it cool completely before glazing.
To make the glaze, heat the heavy cream in a small saucepan over medium heat until it just begins to simmer.
Remove from heat and pour over the chopped semi-sweet chocolate in a heatproof bowl. Let sit for 2 minutes, then stir until smooth and glossy.
Drizzle the chocolate glaze evenly over the cooled bundt cake.
Allow the glaze to set for 15 minutes before slicing and serving.