Melt the butter in a medium pot over medium heat. Add vanilla extract and cornstarch and whisk.
Stir in the granulated sugar, brown sugar, cinnamon and salt and stir once again.
Let the sugar melt down for 5 minutes, stirring.
Then add the peaches.
Stir and cook for 10-12 minutes or until the peaches become cook down, become soft and the filling has thickened. Be patient here, it just takes time and you can't rush it. Don't walk away from the pot since it needs to be stirred regularly.
Remove the pan from the heat and bake in a crust or let it cool completely before storing in an airtight container in the refrigerator for up to 5 days.