In a large pot, over low heat melt butter. Add marshmallows. Stir occasionally until gooey. This takes a little time as you need to keep your heat low or the marshmallows can burn to the bottom of the pot.
Remove from heat and stir in vanilla (eyeball it...a little more doesn't hurt).
Pour in rice krispies and stir until combined.
Spray a 9x13" pan with cooking spray.
Pour rice krispies into pan. With buttered hands press down until even. Set aside to cool.
Pour white chocolate into microwave safe bowl and microwave 40-60 seconds or until softened, stirring at 20 second increments.
Add drops of your food colouring, stirring after each addition until you reach your desired colour.
Pour melted chocolate over rice krispies, spreading for even consistency.
Top with your favourite ghoulish sprinkles.
Allow to cool in refrigerator for 30 minutes for chocolate to set up.
Adding in extra marshmallows makes these rice krispie treats ooey gooey delicious.
When using a 9x13 pan this recipe makes 15 large squares. You could easily double the amount of squares by cutting them smaller.