Prepare a 9X13 inch baking dish with cooking spray and set aside.
In a large saucepan over low heat, melt the butter. Then add the milk,vanilla extract and the mini marshmallows. Stirring constantly, melt marshmallows over low heat until they are fully melted. This may take around 5 minutes. Remove the pan from the heat.
Next, stir in the rice krispie cereal until it's fully mixed in.
Pour the mixture into the prepared pan, gently pressing the mixture down. (Don't press too hard, as this can make the treats hard.)
Let it cool and stiffen, an then cut into squares and enjoy!
Notes
These result in soft, thick treats! You can use a larger pan if you prefer treats that are thinner.Tip: Grease whatever you use to gently press the treats in, with cooking spray to prevent sticking.How to store leftovers:Store any leftover rice krispie treats in an airtight container or plastic bag. Make sure it is sealed the best way possible, to help the treats stay soft and fresh for as long as possible.Wrap properly in freezer paper and in a freezer bag or freezer container for up to 1-2 months. Remove from freezer and allow to call at room temperature and then enjoy.