Combine cocoa, coffee, and boiling water in a bowl, stirring until smooth. Set aside to cool.
Beat 1 1/2 cups butter at medium speed with an electric mixer about 2 minutes or until creamy. Gradually add sugars, beating 5 to 7 minutes. Add eggs, 1 at a time, beating just until yellow disappears.
Add sour cream and vanilla to cooled cocoa mixture. Combine flour, baking soda, and salt; add to butter mixture alternately with cocoa mixture, beginning and ending with flour mixture. Stir in 1 cup chocolate morsels. Pour batter into a heavily greased and floured 10" x 3 1/2" (12-cup) Bundt pan. (Pan will be very full.)
Bake at 350° for 1 hour and 5 minutes or until a long wooden pick inserted in center comes out clean. Cool in pan on a wire rack 15 minutes; remove from pan, and cool on wire rack.
Meanwhile, combine remaining 1 cup chocolate morsels and 1/4 cup butter in a small saucepan; cook over low heat until melted. Remove from heat; stir in whipping cream. Let glaze stand 45 minutes.
Place cooled cake on rack over wax paper. Pour chocolate glaze over cake; spoon any excess glaze on wax paper over cake. Sprinkle with pistachios.