Preheat oven to 350°F (180°C). Grease 5 molds of muffin pan with butter.
Melt the chocolate and butter. In the microwave: break up the chocolate and, together with the butter, heat in a microwave-safe bowl at 600W for 40 seconds and stir. Repeat until nearly all of the chocolate is melted, then stir until the mixture is completely smooth. On the stove: place broken-up chocolate and butter in a large glass or metal bowl and heat over a water bath until melted. Remove from heat and cool.
In a mixing bowl, beat eggs, powdered sugar and salt for 1-2 minutes with an electric hand mixer until thick and fluffy. Beat in cooled chocolate mixture. Then beat in the flour.
Divide batter among the buttered muffin pan molds. The muffin molds will be completely full.
Bake Lava Cakes for 7-9 minutes. The Lava Cakes are done when the edges look dry and are firm while the middles are still very soft and look shiny and gooey.
Immediately either tip the Lava Cakes onto a serving platter or carefully lift them out using a butter knife or spoon. Serve warm.
Notes
Easy make-ahead tip: bake the Lava Cakes in the muffin pan as directed above and allow them to cool completely. Chill. Remove cold Lava Cakes from the muffin pan and store them in an air-tight container in the refrigerator. Before serving, gently warm the lava cakesfor a few minutesin a hot oven until they are jiggly to the touch. You can also warm them in a microwave for 10-20 seconds. Serve immediately with vanilla ice cream, warm Salted Caramel Sauce and fresh raspberries.For classic Lava Cakes in individual ramekins, recipe yields 3 Lava Cakes and baking time will be 10-12 minutes.