BROWN SUGAR PASTRY:

1 c. all-purpose flour
1/4 c. firmly packed light brown sugar
1 oz. unsweetened chocolate, grated
1/2 c. (1 stick) well-chilled butter, cut into 1/2 inch pieces
2 tbsp. milk
1 tsp. vanilla

BROWNIE FILLING:

3 oz. unsweetened chocolate
3 oz. semi-sweet chocolate
1/2 c. (1 stick) butter, cut into tablespoon-size pieces, at room temperature
1 1/2 c. sugar
3 eggs, beaten to blend
2 tsp. vanilla
1/2 c. chopped walnuts
3/4 c. all-purpose flour

CHOCOLATE ICING:

4 oz. semi-sweet chocolate, melted
1/4 c. (1/2 stick) butter, at room temperature
2 tsp. vegetable oil

FOR PASTRY: Combine flour, brown sugar and grated chocolate in large bowl. Cut in butter until mixture resembles coarse meal. Mix in milk and vanilla with fork until just blended. Pat pastry onto bottom and sides of 11-inch tart pan, flouring fingertips as necessary if mixture becomes too sticky.

FOR FILLING: Preheat oven to 350 degrees. Melt chocolates in top of double boiler set over hot water. Remove from heat and stir in butter 1 piece at a time. Transfer mixture to large bowl. Add sugar and blend well; mixture will be granular. Add beaten eggs 1/3 at a time, blending well after each addition. Mix in vanilla. Stir in chopped nuts.

Gradually add flour, blending well after each addition. Pour into pastry shell. Bake until center is just set and tester inserted in center comes out clean, 20 to 25 minutes. Let tart cool on wire rack.

FOR ICING: Combine chocolate, butter and oil in large bowl and mix until smooth. Cool to spreadable consistency, whisking occasionally. Spread icing over top of tart. Let stand until icing sets. Cut into wedges to serve.