Butter an 8x8 inch pan.

In the top half of a double boiler, melt the 3 cups semisweet chocolate chips, 1 cup white chocolate chips, and 1/4 cup butter until soft enough to stir.

Stir in the confectioner's sugar and Irish cream until mixture is smooth. Stir in nuts. Place mixture in the prepared pan and lay a sheet of plastic wrap over top; press and smooth top down.

In the top half of a double boiler melt remaining chocolates until soft. Remove from heat and with a fork beat in the butter and Irish cream until smooth.

Spread topping over cooled fudge with a knife. If a smooth top is important place plastic wrap over the top.