First, make sure your butter is at room temperature and the cream is warm (microwave for 1 minute). This is very important!

Measure out all of your ingredients and set them next to your stovetop.

In a medium heavy-bottomed saucepan, add the sugar in an even layer and melt down over medium heat.

Using a rubber spatula, nudge around the sugar occasionally at first, as it will take about 3-5 minutes to see any changes. As clumps start to form, gently stir until it’s completely melted down (about 5 minutes, or longer if using an electric stove top).

Once melted, it should be golden in color (if it is already a dark amber color, skip this step). Stop mixing and allow it to caramelize and darken. It will only take about 30 seconds for it to turn a rich amber color. Don’t step away from the stove as this happens quickly.

Remove from heat and quickly whisk in the butter all at once. Whisk for about 30 seconds (it may not fully combine but that’s OK).

Quickly pour in the heavy cream and whisk again. Keep whisking until it’s smooth and fluid. If yours clumps up, simply return the caramel to medium heat and keep whisking until it smooths out.

Last, whisk in the vanilla and salt.

Pour into a heat safe container and place the caramel in the refrigerator to chill while we make the cupcakes.

Preheat the oven to 350F and place 12 cupcake liners inside a cupcake tin.

In a medium bowl, whisk together the flour, cocoa powder, espresso powder, salt, and baking soda. Set aside.

In a large bowl using a hand or stand mixer with the paddle, mix together the butter and sugar until light and fluffy. About 3-4 minutes.

Mix in the eggs one at a time, followed by the vanilla and sour cream.

Mix in half of the dry ingredients then scrape down the bowl. Then mix in the Guinness, followed by the rest of the dry ingredients.

Evenly distribute the batter between your 12 cups and bake for 15-17 minutes or until a toothpick comes out clean.

Let them rest for 10 minutes then remove the cupcakes and place on a cooling rack. NOTE: the cupcakes bake flat on top so don’t be alarmed if yours deflate a bit out of the oven.

Using a hand or stand mixer with the whisk attachment, add the caramel and whip on high speed until it forms soft peaks and lightens in color (about 2-3 minutes).

Add the butter and whip again until smooth.

Scrape down the bowl and whisk in the powdered sugar one cup at a time.

Then mix in the heavy cream.

The frosting should be rather thick and fluffy at this point. Scoop about a cup of buttercream into a heat-safe dish and microwave for 30 seconds to melt.

Pour the melted buttercream back into the rest of the batch and mix until smooth. This is a really great trick I like to use to make incredibly smooth buttercream.

Frost the cupcakes when they’ve completely cooled. Drizzle the remaining caramel on top and finish with a pinch of flaky sea salt. Enjoy!