1. Heat the milk in a small saucepan until just boiling.
2. In the top of a double boiler, mix brown sugar, flour, and salt.
3. Then slowly add scaled milk to flour mixture.
4. Stir until thick and then cover and cook for an extra 10 min, stirring occasionally.
5. Add about 1 T of mixture to egg yolks, then add eggs to mixture.
6. Cook for 1 minute and remove from heat.
7. Allow butter and vanilla to melt on top while the mixture cools for a few minutes.
8. Mix all together and pour into baked pie shell.
9. Allow to set.