Preheat the oven to 350°F. Line a 9-inch pie plate with parchment paper and place it on a baking sheet. It will be easier when it will be filled.
Add 1/4 of the milk on the blender with whey protein, vanilla extract, and 2 tablespoons of xylitol. Blend until well combined. Pour it in a medium bowl.
In a saucepan, add the rest of the milk and heat over medium heat until hot but not boiling. Lower the heat to the lowest setting and whisk in the gelatin one tablespoon at a time until fully dissolved. Pour the milk in the bowl with the rest of the ingredients. Stir well to incorporate the ingredients together.
Pour the mixture into the pie plate. Bake for 5 minutes and sprinkle a tablespoon of xylitol over the flan. Bake for another 30 minutes. Let it cool and refrigerate for about an hour for the gelatin to settle.