Preheat the oven to 350 and prepare an 8 inch square pan by lining it with parchment paper or foil.
Place the butter and chocolate in a microwaveable bowl and microwave at 50% power in 30 second bursts, stirring in between, until chocolate is mostly melted. Stir until completely smooth.
In a large bowl, combine the butter and chocolate mixture with the sugar and stir. Add the vanilla and the salt and stir. (The mixture will look grainy but uniform.)
Add the lightly beaten eggs to the mixture and stir until just combined. Add the flour and stir gently until just combined.
With a light touch, carefully fold in the nuts and the chocolate chips. Scrape the batter into the prepared pan and bake for 20 to 25 minutes. Brownies are done when a toothpick inserted in the middle comes out with moist crumbs but no wet batter attached.