Mix together the graham cracker crumbs, melted butter, and sugar in a medium bowl. Press into a 9-inch pie plate to cover the bottom and about 2/3 way up the sides. Refrigerate for at least 10 minutes while you prepare the filling.
To make the pie:
Preheat the oven to 350 degrees F.
Add the squash, milk, honey, eggs, egg yolk, pumpkin pie spice, and vanilla to a large bowl. Stir together with a whisk or a hand-held electric mixer.
Pour into the prepared pie crust and bake for 55-65 minutes or until the filling is mostly set and firm to the touch. (The center may still be a little less firm than the edges; It will continue to cook a little as it cools.) After about 30 minutes of cooking, place a tented piece of foil over the pie to prevent the crust from over-browning or use a pie crust shield.
Let cool fully.
Slice and serve at room temperature or chilled with ice cream or whipped cream, if desired.
Notes
You can make this pie up to a day ahead and store covered with plastic wrap in the fridge or at room temperature.