Preheat oven to 350 F. Grease an 8x8-inch baking pan.
In a large saucepan, melt butter and peanut butter together over medium-low heat.
Once butter and peanut butter have melted, remove pan from heat.
Stir in vanilla.
Add flour, oats, sugar, baking soda, and salt, and stir until mixture forms crumbles.
Press half of the crumbles into the greased pan to form a crust.
Bake for 10 minutes.
Remove from oven, and pour half salted caramel sauce over hot crust. Spread gently if necessary. Leave about a half inch border of crust with no caramel sauce around the outside edge.
Sprinkle marshmallows and then chocolate chips over caramel sauce.
Drizzle remaining half caramel sauce over marshmallows and chocolate chips.
Top with remaining half crumble mixture and pinch of salt.
Bake for an additional 20 minutes, or until lightly golden brown.
Let bars sit for at least 10 minutes before serving.