Preheat your oven to 350°F (175°C) and grease and flour two 9-inch round cake pans.
In a large mixing bowl, combine the all-purpose flour, granulated sugar, cocoa powder, baking powder, baking soda, and salt. Mix well.
Add the buttermilk, vegetable oil, eggs, and vanilla extract. Beat on medium speed for about 2 minutes until well combined.
Carefully stir in the boiling water and gently fold in the toffee bits.
Divide the batter evenly between the two prepared cake pans and bake for 30-35 minutes.
Allow the cakes to cool in the pans for about 10 minutes, then transfer to wire racks to cool completely.
Prepare the whipped cream topping by whipping the heavy cream with powdered sugar and vanilla extract until soft peaks form.
Assemble the cake by placing one layer on a serving plate, spreading whipped cream on top, sprinkling with toffee bits, and adding the second layer. Frost the top and sides with remaining whipped cream and garnish with more toffee bits.