In a large pot over low heat, melt butter. Add mini marshmallows and stir until completely melted and smooth.

Remove from heat and fold in Fruity Pebbles cereal until fully coated.

Working quickly, scoop cereal mixture and form into taco shapes by pressing over a rolling pin or taco mold. Let cool and set.

In a bowl, beat softened cream cheese until smooth. Add powdered sugar and vanilla, beat again until creamy.

Whip heavy cream in a separate bowl until stiff peaks form. Fold into the cream cheese mixture.

Spoon or pipe the cheesecake filling into the cooled Fruity Pebbles taco shells.

Chill for at least 30 minutes before serving.