Preheat the oven to 400 (F) and prepare your egg tart molds by spraying generously with cooking spray.

First, make the filling. In a medium bowl, whisk together 4 large egg yolks, 1/3 cup granulated sugar, 1/3 cup pumpkin puree, 1/3 cup coconut milk and 1/4 teaspoon ground cinnamon until fully incorporated — the mixture should be a bright yellow color. Set aside while you prepare the tart crusts.

Roll out your puff pastry sheet onto a well-floured surface and use your 2 1/2-inch round cookie cutter to stamp out 20 puff pastry circles. Use your hands to gently press the rounds into the egg tart molds by firmly pressing on the bottom and the sides of the molds — but be careful not to overstretch! The puff pastry circles won't cover the molds entirely, and that's okay. Use a fork to poke holes at the bottoms and sides of the puff pastry. Place each puff-pastry lined egg mold on a large baking sheet.

Carefully pour the filling into each puff pastry-lined egg molds, filling each to about 80% full. Transfer the egg tarts into the preheated oven and bake for 20 minutes, until the crust and filling are both puffed. At first the filling will look like it's too puffy and dry, but the center of each egg tart should have a custard/flan-like texture. Transfer to a wire rack to cool for a few minutes, before serving immediately — the egg tarts are best when served warm and only remain fresh for a few hours before they turn soggy and stale.