Instructions

1. Prepare the fruit: Wash and chop the strawberries and rhubarb into small pieces. Place them in a large heavy-bottomed saucepan.
2. Cook the mixture: Stir in the lemon juice and pectin. Bring the mixture to a full rolling boil over medium-high heat, stirring frequently.
3. Add the sugar: Stir in the granulated sugar all at once. Return the mixture to a full rolling boil and cook for 1 minute, stirring constantly. Add the butter if using.
4. Check the consistency: Remove the pan from the heat and skim off any foam. Let the jam rest for a few minutes until it slightly thickens.
5. Jar and cool: Carefully ladle the hot jam into clean sterilized jars, leaving about 1/4 inch of headspace. Seal the jars and cool completely before refrigerating, or process in a boiling water bath for long-term storage if desired.