Makes 1 1/2 cups Delicious raspberry curd, store in the fridge for up to 2 weeks.
Cook frozen raspberries with 1/4 cup water until soft. About 10-15 minutes.
Process in a small chopper or use immersion blender to break up the mixture.
Press through a fine mesh sieve. To extract the most out of the raspberry wrap the mixture into a double layer cheesecloth and twist the pouch until you no longer see raspberry liquid dripping into a bowl.
If puree is too liquidy, heat it again and simmer for 10 minutes until it thickens slightly. Let cool and store in the fridge or freeze.
Beat room temperature butter with sugar, until smooth, add lemon zest, lemon juice, egg yolks, pinch of salt and raspberry puree. Mixture will look curdled.
Pour the mixture into a non reactive sauce pan(stainless steel). Attach a candy thermometer and monitor temperature as you cook raspberry curd. Cook it on low heat. Make sure you heat it slowly. You don't want it to boil as it may curdle. Keep it under 170F, as it reaches 170F it's done.
It the mixture appears too thin even at 170F, keep cooking, stirring frequently and keeping at 170F or slightly under. Mixture thickens and deepens in color as it cooks.
Simple Test - coat the back of the spoon and run a finger across the spoon. If it holds the trail then it's done.
Raspberry curd can be be made ahead of time. Store it in the fridge in an airtight container, for up to 2 weeks.
You can also process raspberry curd in jars, in a water bath for 15 minutes. Raspberry curd treated this way will last longer. Refrigerate for up to 3 months. Once opened, it's good for up to 2 weeks.