Preheat oven to 350.
Butter and flour two 9-inch cake pans.
Sift together the dry ingredients in a bowl. In a large bowl, cream the butter and sugar with an electric mixer at medium speed until light fluffy. Add the vanilla and blend. Beat in the eggs, one at a time. With the mixer on low speed, slowly add the buttermilk. Add the flour mixture in batches, mixing on low speed until completely incorporated. Scrape down the sides of the bowl and mix again. Fold in the chocolate chips.
Divide the cake batter evenly between the cake pans and tap on the counter to remove air bubbles. Bake 35-40 minutes until golden brown and a wooden pick inserted into the center comes out clean of cake batter.
Allow to cool in the pan for 10 minutes, then turn out onto a rack to cool completely before frosting.
In a heavy saucepan, bring the cream, espresso powder and sugar to a simmer over medium heat. Reduce heat to low and stir, about 6 minutes, until the sugar melts completely and the mixture thickens slightly.
Add the chocolate, butter, vanilla extract and salt to a mixing bowl. Pour the hot cream mixture on top. Allow to come to room temperature, stirring occasionally.
Set the mixing bowl with the chocolate inside a larger bowl with a layer of ice cubes on the bottom. Beat the chocolate, using a handheld mixer, until thick and glossy. Scrape the sides of the bowl with a spatula until combined.