1. Preheat oven to 350 degrees Fahrenheit (180 degrees Celsius). Grease and flour a Bundt pan.
2. Pour the boiling water into a measuring cup and place the broken chocolate pieces inside. Stir until chocolate is melted. Set aside to cool.
3. Combine the flour, confectioners’ sugar, cocoa powder, and salt in a medium-sized bowl.
4. In a large mixing bowl, beat the margarine, sugars, and vanilla on medium speed for three minutes until light and fluffy. Scrape the sides of the bowl.
5. Add in one egg at a time and beat until combined. Pour in the chocolate mixture and beat for 30 seconds. Slowly add in the dry ingredients and beat until incorporated.
6. Transfer the batter to the Bundt pan. Gently tap the pan on the counter to level out the batter.
7. Place pan in the center rack of the oven. Bake for 45 minutes.
8. Remove from oven. Allow the cake to cool 10 minutes, then turn out onto a wire rack. Cool completely (about two hours) before glazing.
9. To make the glaze, combine all ingredients in a medium-sized bowl. Whisk until smooth. Allow the glaze to sit for five minutes before pouring over the cake.