OK, I’ll do SMBC, since that is my favorite.
Silk Meringue Buttercream Tips
Flavors- My favorite flavors to blend with the custard base of SMBC are all of the caramel variations (praline, caramel, burnt orange and coffee-caramel), plus apricot. This is a time-consuming buttercream to make, so I usually double or triple a batch of the caramel flavor and freeze whatever I don’t use. Then it’s easy to make any of the caramel variations later by adding in the appropriate flavoring (for praline, I add in hazelnut paste rather than praline paste, since the caramel is already there).
Because this buttercream is denser/richer than mousseline, yet lighter than classic, I like to pair it with cakes of medium density. The Cake bible pairs it with golden genoise (“Golden Cage”), chocolate butter cake (with burnt orange), or brioche-rum cake (“La Brioche Cake”). I also like it with genoise riche or downy yellow butter cake.
Caramel- For the caramel variations, use regular, ultra-pasteurized milk and don’t do anything to make the sugar/milk mixture too acidic, or the milk will curdle as you heat it. This includes using brown sugar or making the caramel too dark (caramelized sugar gets more acidic as it darkens). Also, don’t add cream of tartar to the caramel (an acid). If you haven’t poured liquids into hot caramel before, they bubble up furiously. Use a pan large enough to accommodate this, stand back, and use a heat protective mitt to avoid steam burns. If you want to gently boost the caramel flavor, increase the sugar that you are caramelizing by 25g (per batch) and pour this amount out onto a silpat or foil before adding the milk (I put the silpat on my scale and pour). Break this up and grind it into superfine sugar just before you begin making the meringue. Use it to add to the soft peak whites when making the Italian Meringue.
Creme Anglais- For the custard, the milk must be heated higher than 160 but not above 180 or the eggs will curdle (as per Cake Bible instructions). If only slight curdling has occurred, you can pour the custard into the blender to smooth it out, then strain into a bowl for cooling. Be sure to bring it to room temperature before adding it to the butter.
Italian Meringue- Eggs are easier to separate when cold, but the whites should be whipped when room temp or a little warm. Use an accurate thermometer for the sugar syrup (check it in boiling water). Lower the heat as the sugar syrup approaches 248F, then pour directly from pan to bowl in a thin stream with mixer on high. If you overshoot and end up with too-hot syrup, add a little water, swirl, and bring back to 248F. Scrape the pan with a spatula, you need all the syrup. If blobs of hardened syrup form, work more quickly so the syrup doesn’t cool too much. If you need to cool the meringue quickly (mine always takes forever to cool), use a water bath attachment or place the mixer bowl in a bowl of shallow cool water and whisk by hand or with a hand-held mixer.
Beating and re-beating- For maximum fluffiness, don’t beat the buttercream very much after adding the meringue. For the same reason, add flavorings (especially heavier ones like hazelnut paste or apricot puree) after the custard and before the meringue. Nothing bad will happen if you add the flavorings at the end, the texture will just be a little denser.
This buttercream re-emulsifies when rebeaten after storing, it can be stressful if you haven’t seen it do this before. It thins a bit if you don’t rebeat it, and when you do, it curdles but then comes together into a smooth, beautiful buttercream. Half a minute of hand whisking is usually enough to re-emulsify. I actually love this re-beaten texture for its incredible smoothness, but it isn’t quite as fluffy as when it is first made.
Lastly, as the Cake Bible states, this buttercream holds up at room temperature better than classic, but not quite as well as mousseline. Because of the yolks, it is more yellow than mousseline, though paler than the classic.
I’m probably not the best person to do Mousseline tips, mine always curdles dramatically, and though it seems perfectly fine in the end, it stresses me out and makes me wonder where I might have gone wrong…