Place 2 small plates in freezer to chill. In large saucepan, bring raspberries, sugar, and lemon juice to a boil, stirring often, over medium-high heat. Boil until raspberries have broken down and released their juices, about 5 minutes.

Whisk in chocolate until completely melted, about 1 minute. Continue to boil mixture, stirring and adjusting heat as needed, until thickened and registers 217-220 degrees, about 3-5 minutes (FYI mine took much longer than that to reach temperature). Remove pot from heat.

To test consistency, place 1 teaspoon jam on chilled plate and freeze for 2 minutes. Drag your finger through the jam on plate' jam has correct consistency when your finger leaves distinct trail. If runny, return pot to heat and simmer for 1-3 minutes longer before retesting

Meanwhile, place two 1-cup jars in a bowl and place under hot running water until heated through, 1-2 minutes. Shake dry.

Using funnel and ladle, portion hot jam into hot jars. Let cool to room temperature, cover and refrigerate until jam is set; 12-24 hours. Jam can be refrigerated for up to 2 months.