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This may sound counterintuitive, but when it comes to fruit-flavored buttercream, stay the heck away from fresh fruit. It's hard to resist those baskets of glistening strawberries at the farmers market or a quart of blueberries from the local u-pick, but they're better served in various crisps, cobblers, pies, and galettes—applications where fresh fruit can really shine.
What else do those desserts have in common? Starch and boiling hot temperatures, a one-two punch for managing the water content of fresh fruit in dessert.
Dump a few cups of fresh fruit purée into a basic buttercream, and what you'll have is soup. There's just nothing there to keep all that water in check. Try using less and the fruit's flavor simply won't come through. That's because fresh fruit is mostly water. It doesn't taste like "mostly water" when you're eating a fat, ripe strawberry, but when it's diluted by all the butter and sugar that go into a frosting, that flavor gets lost.
Jams aren't much better. Ounce for ounce, you're spooning more sugar than fruit into the mix, throwing off the flavor and structure of the frosting. Sugar-free fruit reductions aren't as bad, but their flavor is cooked, not fresh.
That's where freeze-dried fruit comes in.
It's pure fruit, minus the water, with no added sugar and a manufacturing process that avoids heat altogether, keeping its flavor fresh and bright. Unlike leathery dried fruit, freeze-dried can be ground into a fine, dry powder that dissolves readily in liquids. Because it contains no water or added sugar, it won't wreck the buttercream's consistency or sweetness.
Brick-and-mortar supermarkets like Trader Joe's or Whole Foods and even Kroger produce their own house brands, while many other groceries sell freeze-dried fruit from companies like Karen's Naturals and Natierra.
Shop online at Amazon and you'll find freeze-dried versions of all the supermarket basics (berries, banana, apple, mango, tangerine, cantaloupe) as well as specialty fruit flavors like dragon fruit, pomegranate, goji, black raspberry, and even durian.
Which is to say, choosing freeze-dried fruit over fresh isn't going to limit your options when it comes to buttercream. The method is super-simple: Start with freeze-dried fruit and grind it in a food processor until powdery and fine. With seedy fruits like raspberry, you may want to sift the powder before use.
The sugar in a Swiss buttercream can be swapped out for flavors that complement the fruit (such as caramely toasted sugar for freeze-dried apples or palm sugar for freeze-dried mangoes), while the liquid sugar in an Italian buttercream can do the same (think honey with freeze-dried banana or agave syrup with freeze-dried pineapple). And on those occasions when you want the focus to be fruit and fruit alone, plain white sugar for Swiss and corn syrup for Italian will keep the canvas neutral.
Technically, French buttercream works equally well, but its pronounced custard flavor can be a distraction from the fruity brightness. Likewise, the strong dairy notes of a German buttercream can subdue the vibrancy of fruit, although this can be used to strategic effect for flavors like Creamsicle or peaches 'n' cream.
Whatever you choose, prepare the buttercream according to the recipe, including any textural or temperature-based adjustments at the end (e.g., if the buttercream is too stiff and cold, it should be warmed and re-whipped before adding the freeze-dried fruit).
Freeze-dried fruit should only be added to a buttercream that's smooth, glossy, and light. If it's too cold or dense, it will be difficult to evaluate the freeze-dried fruit's effects on its flavor and consistency.
Once the buttercream has been prepared, whip in the freeze-dried fruit powder to taste, bearing in mind that its flavor will intensify a little over time as the freeze-dried fruit hydrates and dissolves into the frosting.
Most buttercream recipes can handle up to 2.5 ounces of freeze-dried fruit; it may not sound like much, but this is the equivalent of adding roughly 25 ounces of fresh strawberry purée. Freeze-dried fruit is potent stuff!
So potent, in fact, that it will thicken and stabilize most frostings to a degree that will allow the inclusion of added liquids, such as flavorful liqueurs, strongly brewed coffee, or tea (brought to room temperature, of course).
For example, a splash of rum pairs nicely with the tropical notes of banana, while floral options such as St. Germain can work wonders with aromatic fruit flavors, like raspberry or apricot. Green tea can highlight the grassy flavor of a peach, and rose water works a particular sort of magic with strawberry.
Let your own cravings and intuition be your guide (if it sounds tasty, it probably is), or consult a book like The Flavor Thesaurus for ideas*.
Once the buttercream has been doctored with freeze-dried fruit (and any added liquids), scrape the bowl and whisk attachment and re-whip a minute more to ensure the frosting is well-homogenized and light.
These fruit-flavored frostings are a brilliant way to brighten up familiar cakes, giving bakers a chance to exercise their creativity. The combinations of buttercream styles, freeze-dried fruit powder, and cake layers are near endless, so don't limit yourself to the specific recipes attached to this post.
If anything, let them be templates for your own experiments with fruity frosting—whether that's a maple-banana buttercream to pair with devil's food cake or a strawberry layer cake smothered in strawberry frosting, or something even more off the wall. The only limit is your imagination.