Preheat your oven to 325°F (163°C) and generously spray a 10-cup Bundt pan with nonstick baking spray.

In a large mixing bowl, sift together the granulated sugar, brown sugar, all-purpose flour, cocoa powder, espresso powder, baking soda, baking powder, and salt.

In a separate bowl, whisk together the eggs, sour cream, Guinness, milk, vegetable oil, and vanilla extract until smooth.

Gently pour the wet ingredients into the bowl with the dry mixture and stir until just combined.

Pour the batter into the prepared Bundt pan, filling it about three-quarters full. Bake for approximately 50 minutes.

Once baked, let the cake cool in the pan for about 15 minutes before inverting onto a cooling rack.

In a stand mixer, beat the room temperature unsalted butter on medium speed until silky smooth. Gradually add the sifted confectioners' sugar, alternating with Baileys, heavy whipping cream, vanilla extract, and salt.

Once your cake is completely cool, spread the Baileys buttercream frosting evenly over the top and sides.

To create the whiskey salted caramel, combine granulated sugar and water in a saucepan over medium-low heat until sugar dissolves.