Pre-heat the oven to 350F. Line a pan with cupcake liners or grease it with butter and flour.

Sift the flour, cocoa powder, baking soda, baking powder, and salt together in a large bowl.

In another bowl, mix the oil, coffee, vinegar, vanilla and sugar.

Pour the dry mixture over the wet ingredients. Whisk briefly, until incorporated.

Distribute the batter evenly in cupcake pan. Bake for 15-20 minutes, until a toothpick comes out clean once inserted in the cakes.

You can use pre-made dulce de leche, or make it at home. To make dulce de leche at home, you take many different approaches.

My favorite way to make dulce de leche starts with an unopened can of condensed milk. Place the sealed can in a pressure cooker with enough water to cover it plus at least 2 inches.

Then, bring the water to a boil and cook under pressure for 35 minutes.

Let the pressure release naturally and let the condensed milk can and water cool down all the way before removing and opening the can.

When you open the can, it will be a thick darkened caramel inside.

Place the contents in a container and put it in the fridge until cold and firm.

Remove the butter from the fridge 1 to 2 hours before you start to make this recipe (depending on how warm the kitchen is). We are looking for the perfect butter temperature and consistency. It shouldn’t be hard cold, and it shouldn’t be so soft that is almost melting or losing shape. Cut the butter into thin slabs and set aside.

Melt the chocolate or chocolate chips in a small bowl by microwaving it for 15 second intervals, stirring in between. Let it cool until no longer warm.

Meanwhile, put the whites and sugar in a heatproof bowl.

Place the bowl on top of a small pot with simmering water.

Whisk the whites and sugar until they temp 140 Fahrenheit. Basically you are looking to melt the sugar granules, and also make it so the egg white is in a safe temperature to be consumed.

Once you achieve that temperature, transfer the syrup to your mixer bowl.

Whip with the whisk attachment for about 2 minutes at medium speed, until the mixture looks white, and thicker. At this point, raise speed to high and continue to whip until fluffy and doubled in size. The meringue should have stiff peaks. It can take anywhere from 5-10 minutes to obtain stiff peaks.

Stop the mixer and check the peaks, so you don’t over whip it.

Once the peaks are stiff, start adding the butter that should be slightly softened.

Add one slab of butter at a time.

Wait for one piece of butter to be incorporated before adding the next one.

This whole process could take about 15 minutes. At this point, the buttercream should be thick with a frosting consistency. If not, refer to the troubleshooting below on the notes.

Then beat for another minute or until completely incorporated.

Make ahead: This frosting can sit at room temperature for up to 1 day. Store in the fridge for up to 4 days, or in the freezer, for up to 2 months. Remember to package it really well in sealed air tight containers, or in a zip loc bag, before freezing.

To use it again, simply let it thaw until it comes to room temperature and beat it briefly to make it creamy again.