Ingredients
- 4 cups blueberries – fresh or frozen
- ¾ cup granulated sugar
- 3 tablespoons cornstarch
- Pinch of salt
- 1 tablespoon lemon juice
- 2 teaspoons vanilla extract (optional)
Instructions
Step 1: Cook the Blueberries
Place the blueberries in a medium saucepan over medium heat. Stir occasionally and let them cook until they begin to release their juices and soften. This usually takes about 7 to 9 minutes. If using frozen blueberries, they may take a bit longer.
Step 2: Prepare the Thickening Mixture
While the blueberries are cooking, whisk together the sugar, cornstarch, and salt in a separate bowl. This ensures that the cornstarch distributes evenly and prevents clumping when added to the blueberries.
Step 3: Combine and Thicken
Once the blueberries have softened, gradually add the sugar and cornstarch mixture to the saucepan, stirring continuously. Keep stirring as the filling thickens, which should take about 2 to 3 minutes. The mixture should reach a glossy, syrup-like consistency.
Step 4: Add the Final Touches
Remove the saucepan from heat and carefully stir in the lemon juice and vanilla extract (if using). The lemon juice brightens the flavor, while the vanilla adds depth.
Step 5: Cool and Store
Let the filling cool to room temperature before transferring it to a glass jar or airtight container. Store it in the refrigerator until ready to use. The filling will continue to thicken as it cools.
Notes
How to Tell If the Filling is Thick Enough
The filling should coat the back of a spoon and have a glossy, smooth texture. If it appears too runny, let it simmer for another minute while stirring constantly.
What to Do If the Mixture is Too Thick
If the filling thickens too much, add a tablespoon of water or fruit juice and stir well. Keep adding small amounts until it reaches the desired consistency.
Preventing Overcooked Blueberries
If blueberries are overcooked, they may lose their shape and turn into a jam-like consistency. To prevent this, remove the saucepan from heat as soon as the mixture thickens.
How to Avoid Clumps in the Filling
Always whisk the cornstarch with sugar before adding it to the blueberries. Stirring continuously while cooking also helps prevent lumps.
Using Frozen Blueberries
There’s no need to thaw frozen blueberries before cooking. Simply add them directly to the saucepan, keeping in mind that they may release more liquid and take slightly longer to cook.
- Prep Time: 2 minutes
- Cook Time: 30 minutes