In a large mixing bowl, whisk together the flour, sugar, cinnamon, and salt.
Add the cold cubed butter to the bowl. Use a pastry cutter or your fingers to cut the butter into the dry ingredients until the mixture resembles coarse crumbs.
In a separate small bowl, mix together the milk and vanilla extract.
Gradually pour the milk mixture into the dry ingredients, stirring until the dough comes together.
Transfer the dough to a lightly floured surface and knead it a few times to ensure it is well combined.
Roll out the dough into a thin sheet, about 1/8 inch thick.
Use a sharp knife or a pizza cutter to cut the dough into small square-shaped pieces..
Place the cut-out cereal pieces onto a baking sheet lined with parchment paper.
Brush with melted butter and the cinnamon sugar mixture.
Bake in a preheated oven at 350°F (175°C) for about 10-12 minutes, or until the cereal is crispy and lightly golden.
Remove from the oven and let the cereal cool completely on the baking sheet. Enjoy in a bowl with milk!
