Mix brown sugar, chopped nuts and flour together in a large bowl. Stir in melted butter and mix with your hands until light and crumbly. Remove 1 cup of the mixture to be used later as a topping. Place remainder in an 8-inch square pan and press firmly. Bake at 350° for about 12 to 15 minutes. Beat cream cheese until smooth with 1/4 cup of sugar. Beat in the egg, lemon juice, milk and vanilla. Pour this onto the baked crust. Top with reserved crumbs. Return to a 350° oven and bake for about 25 minutes. Cool thoroughly, then cut into 2-inch squares. These can be baked the day before. Cover with plastic wrap and keep refrigerated. Makes about 16 cookies.