Stir sugars together. Blend in butter, peanut butter, vanilla and egg. Stir in flour to make a soft dough. Add 1/4 c chocolate chips and mix together.
Press into 8" round cake pan. Bake for 10 minutes at 375 degrees.
Sprinkle with marshmallows and remaining chocolate chips. Bake for an additional 5-8 minutes until nicely browned.
Remove from the oven and decorate with halved strawberries while the tart is still warm.
This recipe will make 2 tarts.