Step 1

Preheat the oven to 350 degrees F.

Step 2

Combine the flour, baking powder, baking soda and salt in a bowl. Set aside.

Step 3

In the bowl of a stand mixer (or use a hand held) cream together the butter, brown sugar and powdered sugar until light and fluffy, about 2 minutes. Add the peanut butter and egg and beat until smooth and combined. Add the mashed banana and vanilla, beating until smooth.

Step 4

Gradually beat in the flour mixture. Stir in the chocolate chips. Line two baking sheets with parchment paper or silpats.

Step 5

When the oven is preheated drop about two teaspoons dough onto the prepared baking sheets.

Step 6

Bake for 7 to 10 minutes and do not over cook. If anything undercook. Cool completely before filling.

Step 7

To make the filling, place the egg whites, sugar, and cream of tartar in the heatproof bowl of an electric mixer (or if you do not have a stand mixer use a regular heat proof bowl). Set over a saucepan with simmering water. Whisk constantly until sugar is dissolved and whites are warm to the touch, 4 minutes.

Step 8

Transfer the bowl to stand mixer fitted with the whisk attachment, and beat, starting on low speed, gradually increasing to high, until stiff, glossy peaks form, 5 to 7 minutes. Add vanilla, and mix until combined.

Step 9

To fill the cookies flip half the cookies upside so the flat side is facing up. Spoon or pipe about 2 teaspoons of the marshmallow frosting onto all the cookies, leaving about 1/4 inch border. Wait 5 to 10 minutes and then top each cookie with it's other half. Line the cookies up in rows on a balking sheet and let the frosting set completely, about 1 hour. Try to tightly line the cookies up so that they are upright and strait. Some of my cookies wanted to slide to the side and I ended up with a few cookies that were crooked.

Step 10

Store in an airtight container.