Adjust oven rack to the middle position and heat oven to 450 degrees. Line 8 cups of a regular size muffin tin with extra large paper liners. (I usually end up with 10 - 12). The liners should extend above the cups to facilitate removal (if papers are foil-lined, remove the foil layer). Coat the papers with vegetable spray.
Melt butter and chocolate in a medium heatproof bowl set over a pan of simmering water, stirring occasionally until smooth; remove from heat.
In another medium bowl, beat eggs, sugar, and salt with an electric mixer until sugar dissolves. Beat the chocolate and flour into the egg mixture.
Divide batter among the muffin cups. Bake until batter puffs but centers are not set, 8 - 10 minutes. Let stand in tin for 5 minutes. Meanwhile, flick raspberries with a little water and roll in sugar to coat.
Carefully lift cakes from tin and transfer to dessert plates, removing paper liners. Top each cake with sugared berries and serve.