Place the egg whites and sugar in the mixing bowl of a stand mixer.

Place it over a hot water bath on the stove.

Stir constantly with a hand whisk until the mixture is hot. The temperature should not exceed 65°C (149°F) then remove from the double boiler. If you don't have a thermometer, you shouldn't be able to feel the sugar grains under your fingers. The mixture should be hot.

Place the mixing bowl on its stand (here, a KitchenAid) and whisk at maximum speed until you get a beautiful, firm, and creamy meringue.

Continue whisking at medium speed until the meringue has cooled.  The bowl should be cool to the touch.

Replace the whisk with the paddle attachment (not compulsory) and gradually add the softened butter in batches while continuing to whisk for a good ten minutes.

The meringue may collapse and risk becoming grainy. Don't be afraid; it's normal. Just keep whisking. The cream will become smooth and creamy.

Scrape the bottom and sides of the bowl several times.

Add coloring, flavoring or cold melted chocolate and continue whisking to blend.

Once the buttercream has set and reached the right texture, continue whipping for 5 minutes on low speed (1). It will be light and smooth.

The cream is ready to use.

Heat some water in a saucepan, on which you'll place your mixing bowl or the bowl of the stand mixer. The bottom of the bowl must not touch the water.

Place the egg whites and sugar in the mixing bowl of the stand mixer. As soon as the water is boiling, put the bowl on the saucepan over low heat.

Whisk with an electric hand mixer at medium speed until a firm and glossy meringue forms. Remove from heat.

Place the mixing bowl of the stand mixer on its stand (KitchenAid) and whisk at speed 8 for about ten minutes to cool the meringue.  If you touch the bowl, it should feel cold, and the meringue should also be cool.

If you want to add coloring or flavoring, this is the time to do it. For the chocolate, add it at the end, once the butter is well incorporated and the cream is smooth. If you don't have a stand mixer, you can use the hand mixer at maximum speed.

Replace the whisk with the paddle attachment (K-beater), reduce the speed to 5, and begin adding the butter gradually while continuing to whisk. You can use only the whisk, but the paddle attachment mixes without deflating the meringue and avoids air bubbles.

Stop the mixer to scrape down the sides of the bowl, then resume whisking at low speed (1) for 5 minutes. Before stopping the stand mixer add the melted, cold chocolate in two batches (if you have opted for a chocolate cream).

Now your cream is ready to use.

Put the buttercream into a piping bag and let it chill in the refrigerator for 10 to 15 minutes to make it easier to use. I used it straight away because it wasn't hot.

You can cover the buttercream with plastic wrap and keep it in the refrigerator until you're ready to use it. You'll need to bring it back to room temperature to soften it a bit before using it. You can whip it a second time .

This buttercream recipe is just toppissime, super airy and very light. I recommend you to try it for smoothing your layer cakes and other cakes.