Lay the walnuts on a rimmed baking sheet and bake for 8 minutes. Let cool, then chop.
While the walnuts are toasting, melt half of the stick of butter. Chop up remaining stick and stir it into the hot butter until completely melted. Let cool completely.
In a large mixing bowl, stir together the flour, sugar and salt. Add the lightly beaten eggs and stir well, then stir in the melted cooled butter, bourbon and vanilla.
Spread toasted walnuts and chocolate chips across bottom of partially baked pie crust, then pour filling over the top and spread to the edges. Set pie on a rimmed baking sheet and bake for 40 to 45 minutes or until it appears set. Let it cool completely. Brush with more bourbon.
Garnish with whipped topping or whipped cream before serving.