coffee and black walnut cake with coffee-mascarpon

Ingredients For coffee and black walnut cake with coffee-mascarpon

• CAKE
• 1 c

  black walnut, toasted, chopped, divided (about 4 ounces, any kind of walnuts will do)
• 1 1/4 c

  sugar, divided
• 1 Tbsp

  instant espresso powder
• 1 1/3 c

  all-purpose flour
• 1/2 c

  cocoa (dutch process is best)
• 2 tsp

  baking powder
• 1/2 tsp

  ground cinnamon
• 1/4 tsp

  baking soda
• 1/4 tsp

  salt
• 10 Tbsp

  unsalted butter, room temperature
• 3 lg

  eggs
• 1 lg

  egg yolk
• 1 tsp

  pure vanilla extract
• 3/4 c

  buttermilk (add more by teaspoons if needed)
• COFFEE-MASCARPONE CREAM:
• 4 1/2 tsp

  instant espresso powder
• 1/4 tsp

  ground cinnamon
• 1 Tbsp

  water
• 1 c

  chilled heavy whipping cream
• 1/2 c

  mascarpone cheese
• 1/2 c

  powdered sugar
• 1/2 tsp

  pure vanilla extract
• 3/4 c

  about 3 ounces black walnut, toasted, chopped
• 1/4 tsp

  ground cinnamon
• 1 pinch

  salt