My friends are getting married next weekend, and I’m making the wedding cake (my first!). After tasting a few options months ago, they decided on a lemon génoise with blueberry mousseline buttercream between the layers and white chocolate mousseline buttercream on the outside.
Yes, the cake will contain added cane sugar. BUT, there is one component that is entirely fruit-sweetened: blueberry purée.
For the tasting, I’d flavored the buttercream with St Dalfour blueberry jam (of which I’m a big fan), but for the actual wedding I wanted to make the blueberry flavor from scratch, just to make it more special, fresh, and less sweet. In her Cake Bible, Rose Levy Beranbaum details her technique for producing raspberry and strawberry purées with exceptionally pronounced flavor and (optionally) no added sugar, so I applied the technique to blueberries, and it worked beautifully.
Blueberry Purée (Adapted from Rose Levy Beranbaum’s “Raspberry Purée” & “Strawberry Purée” in The Cake Bible):
Fresh or frozen blueberries
1 Fine-meshed sieve
1 Bowl that the sieve can rest atop
1 Small or medium saucepan
1 Spatula (preferable heat-resistant silicon)
1 Food processor or hand blender
1 Storage container (preferably glass)
If using fresh blueberries (as I did. If not, you can skip the freezing step and go straight to thawing.): Seal the blueberries in a storage container and freeze them overnight. In the morning, transfer the frozen berries into a fine-meshed sieve, and rest the sieve on a bowl. Let the berries thaw completely. This will take a long time (after several hours, my berries had not yet completely thawed because of the large quantity I was using, so I set them over a bain-marie–just placed the bowl directly on a saucepan containing lightly boiling water–and thawed the berries quickly without exposing them to much heat). Once thawed, cover the berries with some parchment paper and crush all of the berries by hand, then remove the parchment and use your spatula to squeeze as much juice as possible through the sieve. Set the fruit aside in the refrigerator, and transfer the juice to a saucepan. Boil on medium-high heat until reduced to 1/3 of the original volume (I started with 3 cups and ended up with 1 cup). Remove the juice from the heat and add the vodka and lemon juice. Combine the juice and fruit in the food processor and puree until smooth. You’ll end up with a purée of exquisitely beautiful color, as in the above photo.
I used my blueberry purée to flavor buttercream frosting. You can also use it to spread on toast, to bake into coffee cake, to garnish a dessert plate or to top vanilla ice cream (add some water and heat it to use as a sauce). Enjoy!