1. Place chocolate in a blender carafe. In a medium saucepan, combine milk, instant espresso powder, egg yolks, agave syrup and sea salt and bring to a simmer over low heat. Cook, whisking constantly, until slightly thickened, about 5 minutes, then pour mixture into blender to melt chocolate. Add silken tofu and blend until smooth. Pour mousse into eight small ramekins. Chill 2 hours and serve cold, garnished with low-fat plain Greek yogurt if desired.