Preheat the oven to 350F. You will need a 24-count mini cupcake pan. Roll out the premade pie crusts and using circle cookie cutter, cut out circles. Line each mini cupcake tin and gently press the dough using your fingers or the back of a spoon. Re-knead and reuse the dough as needed until all tins are full.
Combine all pie ingredients in bowl and mix until well combined: pureed pumpkin, condensed milk, egg, butter, milk, rum and spices. Fill the mini cupcake tins with pumpkin filling, about 2/3 full. Bake in preheated oven for about 24 to 26 minutes until crust starts turning golden brown. Remove the pan from the oven and let the tartlets cool in the pan on a wire rack.
Place the egg whites into mixer bowl and whisk on high speed for about 2 minutes, just until soft peaks form. Meanwhile, place the 1/3 cup sugar and water into a small saucepan. Heat over medium/low heat until syrup reaches soft ball stage, about 238F. Immediately, start slowly pouring in the syrup into the egg whites with the mixer running on low speed. Then turn speed to high and whisk until egg whites are thick and glossy, about 5 minutes.
Transfer the prepared meringue into pastry bag tipped with a star tip and pipe dollops of meringue onto each tartlet. For more garnishes, try adding toffee bits onto the meringue and drizzle with caramel sauce.