Prepare the Strawberry Mixture:
In a medium saucepan, combine the chopped strawberries, sugar, and lemon juice. Stir to combine, then heat over medium heat until the strawberries release their juices and the mixture begins to simmer, about 5-7 minutes.

Simmer the Jam:
Reduce the heat and let the mixture simmer for 15-20 minutes, stirring occasionally, until it thickens and the strawberries break down. Use a potato masher or fork to mash the strawberries to your desired consistency.

Melt the Dark Chocolate:
While the strawberry mixture is simmering, melt the dark chocolate. In a separate bowl, combine the chopped dark chocolate and water. Microwave in 20-second intervals, stirring between each, until the chocolate is fully melted and smooth.

Combine the Chocolate and Strawberry Mixture:
Once the strawberry mixture has thickened, remove it from the heat and stir in the melted dark chocolate and vanilla extract (if using). Mix until the chocolate is fully incorporated into the jam, giving it a rich, glossy texture.

Cool and Store:
Allow the jam to cool to room temperature, then transfer it to a jar or airtight container. Refrigerate for up to 2-3 weeks. The jam will continue to thicken as it cools.