Blueberry Fudge

Ingredients You’ll Need

• 1 cup (150 g) fresh or frozen blueberries (do not thaw frozen)
• 1 tbsp fresh lemon juice
• 2 tsp cornstarch
• 20 oz (567 g) good-quality white chocolate bars, finely chopped
• 1 can (14 oz / 397 g) sweetened condensed milk
• 3 tbsp (42 g) unsalted butter, at room temperature
• 1 tsp vanilla extract
• 1/8 tsp fine salt

How to make blueberry fudge

1. Step 1.

   Line an 8×8-inch pan with parchment paper, leaving an overhang on two sides.

2. Step 2.

   Make the reduction: stir the blueberries, lemon juice and cornstarch together in a small saucepan over medium heat. Simmer for 8 to 10 minutes, mashing the berries as they soften, until the mixture is thick, glossy and jam-like.

3. Step 3.

   Press the mixture through a fine-mesh strainer into a bowl, scraping the underside of the strainer, and discard the skins. You should have about 1/4 cup of thick purple puree. Cool to room temperature, about 15 minutes.

4. Step 4.

   Set a heatproof bowl over a saucepan of barely simmering water, making sure the bottom of the bowl does not touch the water. Add the white chocolate, condensed milk, butter and salt. Stir often with a silicone spatula for 8 to 10 minutes, until completely melted and smooth.

5. Step 5.

   Remove from the heat and stir in the vanilla. Add about three-quarters of the cooled blueberry puree and fold only 2 or 3 times, just enough to create streaks.

6. Step 6.

   Scrape the fudge into the pan and smooth the top. Dot the remaining puree over the surface and drag a toothpick through it in loose swirls.

7. Step 7.

   Refrigerate for at least 3 hours, until firm all the way through. Lift out with the parchment and cut into 25 squares with a sharp knife, wiping the blade clean between cuts.

Why the berries are cooked first

Fudge made from white chocolate and condensed milk sets because it is mostly fat and sugar with very little free water. Fresh blueberries are about 85 percent water, so folding them in raw would loosen the base and leave wet pockets. Recipes that skip the cooking solve this by using dried blueberries, which works, but the berries stay chewy and the fudge tastes mostly of white chocolate. Cooking fresh or frozen berries with a little cornstarch drives off most of the water and concentrates both color and flavor, so only about 1/4 cup of puree is needed.

Strain the puree

Blueberry skins stay tough even after simmering and show up as chewy flecks in a soft, creamy fudge. Straining takes two minutes and gives a smooth, deeply colored puree that swirls cleanly. Frozen berries work as well as fresh, and straight from the freezer they break down in about the same time.

The lemon juice is not for tartness alone. It brightens the flavor, which would otherwise be flattened by the sweetness of the condensed milk and white chocolate, and it keeps the color a clear purple.

Choose bars, not chips

White chocolate chips are made to hold their shape in cookies, and they often melt into a thick, slightly grainy mass. Chopped baking bars, with cocoa butter listed in the ingredients, melt smoothly. Check the label: if cocoa butter is not there, you are buying a white-colored coating, which will not set the same way.

Melt gently

White chocolate scorches at lower temperatures than dark, and scorched chocolate turns grainy and cannot be rescued. A double boiler keeps the heat gentle. Stir often and take the bowl off the heat when the last few pieces are almost gone; the warmth of the mixture melts them. If you prefer the microwave, use 50 percent power in 30-second bursts, stirring each time.

Swirling without muddying

Fold the puree in only two or three times; the mixture is thick, and each extra stir blends the purple into a uniform lavender. The dotted puree on top gives you a second, bolder layer of swirl. Drag a toothpick through it once or twice, then stop.

Setting, cutting and storing

Fudge made with condensed milk and fruit is softer than classic cooked fudge, and it needs to stay cold. Chill at least 3 hours, or overnight for the cleanest cuts. Cut with a long, sharp knife wiped clean between slices, since the fudge sticks to the blade. Keep the squares in an airtight container in the refrigerator for up to 1 week, with parchment between layers. For a party, take out only what will be eaten in an hour or two, because the fudge softens quickly at room temperature. To freeze, wrap tightly and keep for up to 2 months; thaw in the refrigerator.

Variations

Blueberry lemon: add 1 teaspoon of finely grated lemon zest to the melted chocolate for a more pronounced citrus note.

Berry swap: raspberries or blackberries can be cooked down the same way. Raspberries and blackberries have seeds, so straining is essential.

Crunch: sprinkle a spoonful of freeze-dried blueberries, crushed, over the top before chilling.