Melt the butter in a saucepan over medium heat. Add 1 cup of the chocolate chips and heat for a few seconds more, then remove from the heat. Tilt the pan to make the butter run over the chips. Set aside for 5 minutes. Whisk to smooth the chips.

In a large bowl, combine the eggs, sugars, and vanilla and whisk until evenly blended. Add the melted chocolate and whisk to blend. Add the flour and salt and stir until combined. Add the nuts and the remaining ⅓ cup of chocolate chips. Scrape the filling into the piecrust and smooth the top.

Bake on the center oven rack for 30 to 35 minutes, or until a crust develops and the pie rises slightly. (A toothpick inserted into the center will not come out clean.)

Transfer to a cooling rack. Serve warm.