Preheat oven to 350°F. Grease and flour an 8 inch square baking pan.
In a large bowl, combine brown sugar, flour, and pecans. Stir in melted butter and mix with a fork until light and crumbly. Remove 1 cup of mixture and set aside.
Place remaining crumb mixture in the bottom of the baking pan and press firmly to form crust. Bake 15 minutes.
Cream together the cream cheese and sugar.
Beat in egg, lemon juice, milk, and vanilla.
Pour over baked crust. Top with the remaining crumb mixture.
Bake 25 minutes or until filling is set.
Cool thoroughly. Cut into 1x4 inch bars. Chill.