Line an 8"x8" inch square brownie pan with aluminum foil. Spray the foil with nonstick cooking spray.
Melt butter in a large pot. Once melted stir in 7 cups of mini marshmallows.
Once the marshmallows have *just* melted stir in the red velvet cake mix, kosher salt, vanilla extract, and red gel food color. Mix to combine. Remove from heat and stir in the Rice Krispie cereal and 4 cups of remaining mini marshmallows.
Transfer mixture to the prepared pan and lightly press into an even layer. Don’t press too hard as this makes for hard Rice Krispies treats!
Let set. Slice and enjoy!
Notes
I prefer to use red gel food color because you can use less and it offers a more saturated color. This is the color I used for this recipe. It's called "super red". (This is an amazon affiliate link.)You can use red liquid food color, you'll just need to use a bit more depending on how deep of a red you'd like to achieve. Make Ahead: Stored properly, rice krispie treats stay soft for 3-4 days, so you can easily make these a day or two in advance.Storing: Store leftover red velvet rice krispie treats at room temperature in an airtight container or ziptop bag with all the air pressed out of it for 3-4 days. Do NOT put rice krispie treats in the fridge, as they will harden.Freezing: Unfortunately, rice krispie treats cannot be frozen. While many baked goods can be frozen, thawed, and still be tender and tasty, rice krispie treats never get soft again after being chilled or frozen.