Found this recipe for a single-serve molten cake...easy to double or make more.
3 tsp butter
¼ C chocolate (chips, or chopped)
1 Tbls + 1 tsp sugar
1 Tbls peanut butter
1½ tsp flour
non-stick cooking spray
1 tsp cocoa powder
Preheat oven to 375˚. Spray ¾-cup ramekin with non-stick cooking spray; dust with cocoa powder and set aside.
Using a double boiler or microwave, melt butter and chocolate. (This is a very small amount; if using a microwave, be very careful not to cook your chocolate!)
In a separate bowl, whisk egg, sugar and peanut butter until light and creamy. Stir in chocolate until well incorporated; add flour, stirring until just combined. Pour into ramekin.
Set on baking sheet; bake approximately 10 minutes - a little less for a runnier molten center (about ¾" around the edge will look dull, with the center still moist), slightly more for a creamy yet 'set' center (almost all of the top will look dull/dry).
Let cake cool 2 minutes before serving; cake can be (carefully!) inverted onto dessert plate and dusted with cocoa powder or powdered sugar if desired.