In a medium saucepan over low heat, melt the unsalted butter. Once melted, add mini marshmallows, stirring continuously until smooth and glossy. Remove from heat and fold in Fruity Pebbles until coated.

While the mixture is warm, scoop portions into your hands and shape around a rolling pin or taco shell mold lined with parchment paper. Press firmly for 30 seconds to set, then remove and let cool completely.

In a mixing bowl, beat softened cream cheese until smooth. Gradually add powdered sugar and vanilla extract, beating until creamy. In a separate bowl, whip heavy cream until stiff peaks form, then fold into the cream cheese mixture.

Transfer the cheesecake mixture into a piping bag or use a spoon to fill each taco shell generously. Pack it in well for an indulgent bite. Sprinkle extra Fruity Pebbles on top for garnish.

Place the tacos in the refrigerator for at least 30 minutes to firm up the filling. Serve chilled.