Toast pecans using whatever method you prefer. I like to roast them at 350 for about 8 minutes, then chop them.
Melt butter in saucepan and let cool slightly.
In a mixing bowl, whisk together both sugars and flour. Whisk in eggs, evaporated milk and vanilla, followed by melted butter and toasted pecans. Pour into unbaked pie crust.
Set on a cookie sheet and bake at 325 degrees for 50 minutes. Let cool completely.