Preheat the oven to 350°
In a mixing bowl or stand mixer, beat together butter and sugar until light and fluffy. Mix in the egg and egg white
In a separate bowl, whisk together cinnamon, baking soda, cream of tartar, sugar, salt, and flour in a bowl
Slowly incorporate the flour mix into the butter mix. When fully mixed, fold in cereal and marshmallows
Scoop 1 heaping tablespoon of the dough at at a time onto a lined baking sheet. This dough yields about 20 cookies.
Bake cookies 10-12 minutes or until they being to turn golden brown around the edges.
Remove from oven and let rest for 3-5 minutes, then transfer to a cooling rack until completely cook. Serve immediately or store at room temperature in an airtight container.
