In an 8-quart pan, combine the strawberries, raspberry pulp, lemon juice, sugar, and butter.
Over medium-low heat, stirring constantly, heat the mixture until the sugar is completely dissolved. Increase the heat to medium-high and bring the mixture to a full rolling boil, stirring constantly. Stir in the entire contents of the pectin pouch. Return the mixture to a full rolling boil, stirring constantly. Boil, stirring constantly, for 1 minute. Remove the pan from the heat. Skim off the foam.
To prevent the jam from separating in the jars, allow the jam to cool 5 minutes before filling the jars. Gently stir the jam every minute or so to distribute the fruit. Ladle the hot jam into hot jars, leaving a ¼-inch headspace. Wipe the jar rims and threads with a a clean, damp cloth. Cover with hot lids and apply screw rings. Process half-pint jars in a 200 degree water bath for 10 minutes, pint jars for 15 minutes. Remove to towel-lined surface and let cool for 24 hours without disturbing. Makes 7 to 8 half pint jars.
Recipe by The Culinary Cellar at https://theculinarycellar.com/strawberry-raspberry-jam/