Prepare the pie crust and place in a 9-inch deep dish pie plate.
Whisk the eggs. Mix in corn syrup, sugar, cocoa powder, flour, salt, and vanilla; this keeps melted butter from cooking the eggs or resolidifying. Then, whisk in the melted butter.
Stir in the chopped pecans, then pour into unbaked 9-inch deep-dish pie crust.
Bake at 350F for 55-60 minutes, until puffy and set. The filling will not jiggle or slosh when the pie is done.
Don't just go by baking time; pay attention to doneness cues.
Cool for at least 2-3 hours before serving. Pie will deflate a little and settle as it cools.
Store leftovers, covered, in the refrigerator for up to 3 days.
Notes
You will need a 9-inch deep dish pie crust to make this pie; it's too much filling for a standard pan. I always use my Homemade Pie Crust recipe.I believe you could substitute extra cocoa powder, or a cup-for-cup gluten-free flour blend, for the flour to make this filling gluten-free. Be sure to use a gluten-free pie crust.Golden syrup, honey, and maple syrup can be substituted for the corn syrup; the filling may be looser. Recipe adapted lightly from Taste of Home.