Melt butter in the microwave, and cool.
Once the butter has cooled, add the white sugar, and brown sugar, and mix well on high speed with a hand mixer or stand mixer for 2-3 minutes
Add the eggs and vanilla to the mixture and mix for another 1-2 minutes. The batter should be light colored and fluffy at this point.
Add in the dry ingredients and mix well until all the dry mixture is combined with the wet ingredients. Don't overmix.
Add in the mini marshmallows, crushed cornflakes, and chocolate chips. Fold into the batter just until combined.
Divide the batter into equal balls of dough (I use an ice cream scooper to help). The dough should make about 14-18 cookies.
Place mixture in the fridge for at least 2 hours (ideally overnight if you can wait that long).
Pre-heat oven to 350ºF degrees.
On a cookie sheet lined with parchment paper place cookie dough balls at least 1.5 inches apart.
Place cookie sheet in the oven and bake for 14-18 minutes. The sides should start to brown on the sides but the center will look soft.
Once removed from the oven, rap the cookie sheet on the counter to get that rustic cookie look.
Leave in the cookie sheet to cool for at least 20 minutes. The cookies will be too soft when they are fresh from the oven and will harden as they cool
After 20 minutes move cookies to a cooling rack.
If drizzling chocolate, melt 1 oz. chocolate in the microwave and drizzle on the cookies