Preheat the oven to 350°.
Heat the butter and unsweetened chocolate in a small saucepan over low heat, stirring until melted and smooth.
Remove the pan from the heat and whisk in the sugar until smooth. Pour into a medium bowl and set aside to cool for 10 minutes.
Whisk in the eggs one at a time. Whisk in the flour, vanilla, and salt.
Fold in the chocolate morsels and pecans. Pour into the pie crust.
Bake until just set and a crust forms on top, about 1 hour. Cool to room temperature on a wire rack.
Just before serving, dust with powdered sugar.
To store, wrap tightly and keep at room temperature for up to 2 days.