Ingredients:
1 unbaked 9-inch pie crust (store-bought or homemade)
1 cup warm water
1 cup granulated sugar
4 tablespoons all-purpose flour
1 teaspoon vanilla extract
3 to 4 drops liquid food coloring (optional, traditionally yellow to mimic an egg custard)
Pinch of salt
3 tablespoons butter, cut into small cubes

Directions:
Preheat your oven to 400°F (200°C).
Prepare the crust: Fit your unbaked pie crust into a 9-inch pie plate and crimp the edges.
Mix the liquid base: Pour the 1 cup of warm water directly into the pie crust.
Make the flour slurry: In a separate small bowl, whisk together the sugar, flour, and a pinch of salt until well combined. Gently sprinkle this dry mixture evenly right into the water in the pie crust (do not stir it aggressively, or it can clump).
Add flavor: Drizzle the teaspoon of vanilla extract (and optional food coloring) right into the liquid mixture. Give it one very gentle swirl with a knife or fork just to incorporate everything lightly.
Top with butter: Dot the top of the liquid mixture with the small cubes of butter. As it bakes, these will melt and create a rich, buttery top layer.
Bake: Bake at 400°F for 15 minutes, then lower the temperature to 350°F (175°C) and bake for an additional 45 to 50 minutes.
Cool completely: The pie will look completely watery and jiggly when you pull it out of the oven don't panic! It needs to cool completely at room temperature and then chill in the fridge for a few hours so the flour and butter can set into a translucent, custard-like gel.