Brownie with frosting

This is my 1st attempt for Brownie. I use the recipe from 'A Treasury of CookBook, Classics' by Creative Publising. Anyhow, I replaced the sugar with fruit sugar, but the frosting is a bit too sweet using the icing sugar as stated.

Brownie
Ingredients
2.5 cups (625ml) Butter (can try to add only 1 block of butter, I used 1.5 blocks)
4oz (115g) semi-sweet chocolate chips
4 medium eggs, room temperature
1/4 tsp (1ml) salt
2 cups (500ml) sugar (I replace this with Fruit sugar to 3/4 cup)
1 tsp (5ml) vanilla extract
1 cup (250ml) all purpose flour
1 cup (250ml) walnuts pecans, chopped

Method
1. Preheat oven to 175 degree celcus
2. Grease a 13 X 9 inch baking pan
3. In a double boiler, melt butter and chocolate. Remove from heat.
4. Cool chocolate for 5 minutes
5. Using an electric mixer, beat eggs and salt in a large bowl until lemon colored and foamy.
6. Add sugar and continue beating until mixture is well blended.
7. Stir in vanilla.
8. Add cooled chocolate to mixture.
9. Fold in flour. Do not over mix.
10. Gently fold nuts into batter.
11. Pour batter into prepared pan.
12. Bake for 20 to 25mins until a wooden stick inserted into the center comes out clean.
13. Cool in baking pan.


Chocolate Frosting
Ingredients
4oz (115g) semisweet chocolate
3tbsp (45ml) butter (I used margerine instead of butter)
2.25 cups (675ml) icing sugar, shifted (I reduced the sugar as usual)
1tsp (5ml) vanilla extracts
6tbsp (90ml) light cream (I used whipping cream instead of light cream)

Method
1. In a double boiler, melt chocolate and butter.
2. In a medium bowl, mix icing sugar, vanilla and cream with an electric mixer until combined.
3. Add to chocolate in double boiler. Cook for 5 minutes, If mixture becomes too thick, add a little more cream.
4. Remove from heat.
5. Spread frosting on cooled brownies