Line an 8-inch square pan with nonstick foil or regular foil sprayed with non-stick cooking spray.
Preheat oven to 325º.
Melt the 9 ounces of semi-sweet chocolate, 1 ounce of unsweetened chocolate, and ½ cup of butter in a large, microwave-safe bowl. Stop and stir at 30-second intervals till melted and smooth.
Stir in the sugar, then the eggs and vanilla. Add the flour and salt and mix till well combined. Stir in walnuts.
Pour batter into the prepared pan and smooth the top.
Bake for 35 to 40 minutes or till a toothpick inserted into the center comes out with a few moist crumbs. Cool completely.
To make the glaze, microwave all ingredients in a microwave-safe bowl, stopping to stir every 30 seconds till the chocolate is almost melted.
Stir until the mixture is smooth, then let cool for about 10 minutes before spreading the glaze over chilled brownies.
Place the walnut halves, spaced evenly, over the glaze before it sets.
Chill brownies to cut.
