Place the dates, lemon juice, and fruit into a two-quart stainless steel saucepan over low heat. Stir it every few minutes as the fruit thaws and gradually releases its juice.
Continue cooking over low heat, stirring occasionally, until the mixture is warm and soupy.
Carefully pour the mixture into a high-speed blender and process for about a minute until smooth. Return the mixture to the saucepan over low heat.
Add the chia seeds and continue to cook over low heat for 10-15 minutes, until it begins to thicken. Remove from the heat.
Sterilize a mason jar and pour the mixture into it. Cap and refrigerate until cool. Serve over yogurt, on sandwiches, or with ice cream.