Melt chocolate; cool slightly. Beat eggs; beat in chocolate, honey and vanilla. Thoroughly beat in biscuit mix. Stir in pecans. Pour into greased 12″ x 20″ x 2″ baking pan; bake at 350 degrees F until toothpick inserted in the center comes out clean, about 20 minutes. Cool completely . Spread with frosting; let set up.
Gradually beat 1/2 cup boiling water into 1-1/2 pounds powdered sugar. Beat in 5-oz. melted unsweetened chocolate and 3-oz. (1/4 cup) honey, then 1/2 tablespoon vanilla extract. Thin frosting with 1-2 tablespoons of boiling water, if necessary.