To prepare a cooked strawberry jam desserts recipe, first you need to gather your ingredients. First, you will need the following ingredients: Strawberries, sugar, water, vanilla, and salt. You will also need: 1 cup (240 ml) of boiling water. Place the strawberries and sugar into the saucepan and heat over medium heat, stirring constantly, until the sugar dissolves. Remove from the heat and allow the mixture to cool to room temperature. Then, place the cooled mixture into jars and store in an airtight container in the refrigerator for up to 3 months.