Line an 8" x 8" baking pan with parchment paper and lightly spray with non-stick oil. I like to use 2 strips of parchment paper like a "t" to lift the treats out easily.
In a large pot, melt the 3 tablespoon vegan butter over medium-low heat. Add in the 10 oz bag vegan mini marshmallows and stir continuously until they are completely melted together into one large blobby marshmallow. It takes about 8 minutes. As soon as they become 1 mass, remove the pot from heat and stir in the ½ teaspoon vanilla extract.
Add in the 4 cups rice krispie cereal and stir until they are completely coated with marshmallow. Transfer to the prepared pan and use your hand and a piece of parchment paper to press down to even them out. Set aside.
Next, add the 1 cup non-dairy chocolate chips and 1 tablespoon vegan butter to a bowl and microwave for 20 seconds. Take it out, stir, and continue to microwave in 20 second intervals until its all melted. Make sure you don't overcook the chocolate or else it'll stiffen up.
Spoon the melted chocolate over the rice krispies and spread in an even layer. Sprinkle the 3 tablespoon rainbow candy chips on top and let rest for about an hour. Use the parchment paper to lift the treats out of the pan and cut with a sharp knife into 12 pieces.
Store in an airtight container for up to 3 days. Keep them at room temperature as they don't do well in the fridge or freezer.
Notes
Technically Kellogg's Rice Krispies aren't vegan. They contain vitamin D3 which is made from animals. You can find other brands that are vegan and work well like Nature's Path and store brands.
I use Bakers Choice Rainbow Candy Chips which I order from Amazon.
If you can't find vegan mini-marshmallows, cut up regular sized ones in smaller pieces with scissors.
Make sure you don't brown the butter or the marshmallows! Cook them on low and remove them from heat as soon as they are fully melted.