Butter 2 1/2 to 3 quart soufflé dish.
Place panettone in the bottom of dish.
Heat milk, sugar, and salt in 2 quart saucepan over moderate heat.
Stir until sugar is dissolved, careful to avoid boiling.
Remove from heat and add chocolate, let stand for 2 minutes.
Whisk until smooth.
In a large bowl beat eggs together.
Add chocolate mixture to eggs.
Whisk until combined.
Stir in yogurt and vanilla.
Pour mixture over panettone and let soak at room temperature for an hour.
Preheat oven to 325.
Before baking crumble bits of butter on top.
Place soufflé dish in a large pan and fill up to two inches with water.
Bake 45 minutes to 1 hour, until the edges start to brown but center still jiggles a little.
Serve with a scoop of Stonyfield Organic Caramel Crème Ice Cream