In a medium bowl add ½ cup of milk, flour and egg yolks. Mix until smooth and set aside.
In a skillet or medium-sized saucepan add 2 cups of milk over low heat. Cook just until the milk starts to bubble.
Over medium-low heat add the brown sugar, salt, and ½ cup water to a small saucepan and cook to a gentle boil. Continue cooking until the sugar mixture thickens and starts bubbling.
Slowly add the caramelized sugar to the hot milk stirring constantly. Continue to cook over over medium-low heat.
Slowly whisk in the egg yolk mixture. Continue to cook, stirring constantly until the custard becomes thick. This may take about ten minutes and the custard should coat the back of a spoon.
Take off the heat and add the butter and vanilla, stir to combine. Pour into the prebaked pie shell.
In a large bowl or a stand mixer beat the egg whites and whisk until foamy.
Whisk in the cornstarch and cream of tartar until soft peaks form. Gradually whisk in the sugar until the meringue is stiff but not dry and peaks form.
Spread the meringue over the hot butterscotch filling. Make sure to spread completely to the edges of the pie.
Place in a 350-degree oven for about 8 minutes to brown the meringue.
Let the pie cool completely before serving
After serving lightly cover with plastic wrap and store in the refrigerator. Note: The meringue may weep once refrigerated.
The prep time and cook time does not include the prebaked pie shell.One Hot Oven provides approximate nutritional information as a courtesy and cannot guarantee the accuracy for any recipe on this blog.