Melt butter and chocolate in a medium heat-proof bowl over a saucepan of simmering water; remove from heat. Beat eggs, sugar and salt with a hand mixer in a medium bowl until sugar dissolves. Beat egg mixture into chocolate until smooth. Beat in flour or matzo meal until just combined. (Batter can be made a day ahead; return to room temperature an hour or so before baking.)

Before serving dinner, adjust oven rack to middle position; heat oven to 450 degrees. Line a standard-size muffin tin (1/2 cup capacity) with 8 extra-large muffin papers (papers should extend above cups to facilitate removal). Spray muffin papers with vegetable cooking spray. Divide batter among muffin cups.

Bake until batter puffs but center is not set, 8 to 10 minutes. Carefully lift cakes from tin and set on a work surface. Pull papers away from cakes and transfer cakes to dessert plates.

Top each with sugared raspberries and serve immediately.