Homemade filling does take some time, and the bulk of the work comes in straining your berry mixture through a sieve to remove the seeds. You could leave the seeds in if you want to save time; I’ve certainly done so, but for some treats – like the more delicate lemon raspberry cupcakes pictured in this photo, I think straining is worth it.
If you want to make raspberry filling at a time of year when fresh raspberries aren’t readily available at your local market, you can always use frozen berries. I recommend letting them thaw out first, but you can also pulse them in a food processor to break them down a bit before cooking them.
- 12 ounces raspberries, mashed
- 1 1/2 cups powdered sugar
- 4 teaspoons cornstarch
- 2 teaspoons lemon juice
In a medium saucepan, stir together raspberries, powdered sugar, cornstarch, and lemon juice. Cook over medium heat until the mixture boils, then allow it to boil for 1 minute, stirring well, until the mixture thickens.
Remove from heat and press through a fine sieve to filter out the seeds. Allow to cool before using; makes about 1 cup.