In a small saucepan, add Guinness and bring to a simmer over medium heat. Continue to simmer until the beer reduces to 1/2 cup. Remove from the heat and set aside to cool.
In a large bowl, combine flour, cocoa powder, baking soda, baking powder, and salt. Whisk to combine.
In the bowl of a stand mixer (hand mixing is fine too!), fitted with the whisk attachment, place reduced Guinness, Arbequina EVOO, sugar, eggs, sour cream, and vanilla extract. Whisk until blended and smooth.
To the wet ingredient bowl, slowly add in the dry ingredients (a cup at a time). Continue until batter is smooth and blended.
Line cupcake pans with your baking cups and fill 3/4 of the way full with batter.
Bake cupcakes for 20-30 minutes or until toothpick comes out clean. Remove from the oven and set aside to cool.
Place unsalted butter in the bowl of a stand mixer (hand mixing is fine too!), fitted with the paddle attachment, and beat or cream until smooth. Replace the the paddle attachment with the whisk attachment and begin whisking in the powdered sugar (one cup at a time), until combined.
Add Raspberry (Strawberry/Fig/Pomegranate) Dark Balsamic Vinegar, vanilla extract, cocoa powder, and milk, and continue to whisk until fluffy and smooth.
Once the cupcakes have cooled completely, top with frosting (either spreading or piping frosting on top of the cupcake).
Make sure your cupcakes have completely cooled down; otherwise, the frosting will melt!