Cut six 4-inch circles of parchment paper. Prop up an oven rack on the counter, using cans of vegetables or beans; the rack should be elevated a few inches.
Melt the marshmallows and butter together in a large pot over medium heat. Stir in the cornflakes. Pour the mixture onto a baking sheet.
Using the parchment circles as stencils, cut the corn treats into circles with a paring knife. Leaving the parchment on, mold the circles into a taco shape. Place the tacos, parchment down, into the oven rack so that the bottom of the tacos touch the countertop. (If they don't touch, lay the cans on their sides to lower the rack.) Let the tacos set up for 5 to 10 minutes, or until dried and crisp.
Once the tacos are hardened, fill them with ice cream using a 2-tablespoon scoop, then sprinkle with rice cereal. Freeze until ready to serve. (When freezing, it's best to arrange the tacos snugly in a baking dish so they stand upright.)
To serve, set up a toppings bar of diced strawberries, whipped cream, green shredded coconut and yellow and orange chocolate candies. Invite everyone top their taco with their favorite fixings.