Melt butter, add brown sugar and allow to briefly brown. Gradually add boiling water. In a separate bowl, beat egg yolks. Add small amount of flour alternating with milk to the egg yolks. Keep mixing milk and flour into egg mixture with wire whisk until mixture is smooth. Add salt to egg mixture. Add small amount of hot sugar/water mixture to eggs to temper and whip well. Do this a couple to times to make sure you have tempered the eggs. Then add the egg mixture to the rest of the brown sugar/water mixture on the stove. Cook until thick stirring to prevent scorching. Remove from stove and then add the vanilla. Pour into graham cracker crust and cover w/ meringue. You can also use a precooked pie crust that has cooled.