In a small sauce pot, over medium heat, combine raspberries, vanilla, lemon juice and sugar. Mix well and cook, uncovered, for about 15 minutes, stirring occasionally.
Strain out about 1 1/2 to 2 tablespoons of raspberry liquid for the drizzle. Chill remaining raspberry jam until cold and put it in a piping bag. (You will cut off a small opening at the tip of the piping bag when ready to fill the doughnuts.)
Preheat the oven to 350 and grease a doughnut pan.
In a large mixing bowl, whisk egg, sugar, milk, sour cream, melted butter, and vanilla together until smooth.
Sift in all dry ingredients and whisk until all incorporated.
Break up baking chocolate and put it in a small bowl. Microwave for 45 seconds on 1/2 power. Stir and microwave for 30 more seconds if needed. (Still on 1/2 power.)
Mix melted chocolate into the batter.
Pour the batter into a piping bag. (You may have to pour some batter in and refill later.)
Cut the tip off the piping bag, leaving only about about 1/4 to 1/2 inch opening.
Squeeze batter into the doughnut cups of the pan, in a circular motion, filling them only about 1/2 way. Make sure there is an even amount of batter all around.
Pipe in some raspberry jam in the middle of the batter, in a circular motion, making sure that the jam doesn't go to the edges.
Pipe some more chocolate batter over the jam, covering it completely and filling the doughnut pan cups no more than 3/4 full.
(Refill the piping bag when needed.)
Bake for 15-18 minutes and let doughnuts cool on the wire rack.
Sprinkle with powder sugar and drizzle with strained raspberry sauce.