01 -
Set your oven to 175°C. Butter a rectangular 9x13-inch pan and keep it nearby.
02 -
Use a big bowl to whip the butter along with the white and brown sugars until light and fluffy in texture.
03 -
Toss in one egg after the other, beating each time. Add the vanilla and stir in gently.
04 -
Whisk the flour, baking soda, and salt in a separate bowl, then add the mixture to the wet ingredients little by little until just mixed.
05 -
Gently fold in the chocolate chips, then spread the dough evenly across your greased pan.
06 -
Put it in the oven and bake for 20-25 minutes. The edges should get golden. Let it cool fully before the next step.
07 -
When the base is cool, spread the marshmallow fluff evenly across the cookie dough bottom.
08 -
Microwave the chocolate chips and your butter (or oil) in a heat-safe bowl, stirring every 30 seconds until smooth.
09 -
Pour the silky chocolate mixture over the marshmallow, using a spatula to smooth it out.
10 -
Let the bars set at room temp or refrigerate to harden the chocolate. Slice into squares once firm and enjoy!