Fruit Milkshake Base
1 pound fresh berries (strawberry, blueberry, blackberry or raspberry) or a mixture of any or all
¼ - ½ cup granulated sugar (depending on sweetness)
2 heaping tablespoons fruit jam (strawberry, blueberry, blackberry or raspberry)
2 teaspoons fresh lemon juice
1. Put the berries in a bowl, add the sugar and gently stir to combine. Let the berries sit at room temperature for 30 minutes, until they start to soften and release their juices.
2. Transfer the mixture to a medium nonreactive saucepan, and cook over medium-high heat until slightly softened. Coarsely mash the berries using a potato masher or back of a fork and continue cooking, stirring occasionally, until the mixture thickens to a jam-like consistency, about 20 minutes. Stir in the fruit jam and cook for 1 minute longer.
3. Remove the pan from the heat and stir in the lemon juice. Transfer the fruit base to a bowl, let come to room temperature then cover and refrigerate until very cold, at least 4 hours. The base will thicken further as it chills.