Beat egg yolks; add brown sugar. Make a paste with cornstarch and enough water to moisten. Add this to the eggs and brown sugar, also the salt and milk. Place in a double boiler and cook until thickened, about 20 minutes. Remove from heat and add butter and vanilla. Pour into pre-baked pie shell.

Prepare meringue by using the ratio of 1 tablespoon sugar to 1 egg white. Beat whites until fluffy, then fold in sugar. Spread over entire pie. 

Bake in oven until delicately brown, about 10 minutes at 300° to 325°.