For the haupia layer: Whisk to combine the coconut milk, whole milk, cornstarch, vanilla and sugar in a medium saucepot. Place the pot over medium heat and continue whisking the mixture slowly as the liquid starts to thicken. Once you notice that the liquid is starting to thicken, adjust the heat to low and continue to whisk until the mixture is completely thickened and the texture looks smooth and shiny, about 3 minutes.
Place the pie crust on a plate or baking sheet. Using a small heatproof rubber spatula, pour and scrape the mixture into the pie crust, spreading the mixture out as evenly as possible. Place the plate with the pie into the refrigerator and chill until set, about 30 minutes.
For the passion fruit layer: Combine the passion fruit puree and whole milk in a medium saucepot. Sprinkle the gelatin on top of the liquid and whisk gently to combine. Let this mixture sit for 2 minutes.
Place the pot on the stove on medium heat. Once the mixture starts to warm up, add the sour cream, sugar and gelatin and gently whisk until the sugar and gelatin are completely dissolved. Do not let this mixture boil and do not whisk too much which will produce unwanted foam and bubbles.
Place the entire pot into an ice bath. Using a small rubber spatula, gently stir as the liquid cools. Once the mixture is at room temperature, strain it into a small bowl using a fine mesh strainer to remove excess air bubbles. Pour this over the haupia layer and place in the refrigerator. Chill for at least 4 hours or up to overnight before cutting.
For the garnish: Whisk the heavy cream in a large bowl to stiff peaks. Use a warm knife to cut the pie and serve with the whipped cream and fresh berries.