Whisk together the flour, sugar, and salt in a large bowl. Add the butter and mix with a pastry blender or fork until the mixture resembles coarse meal and the butter is the size of small peas. (You can also do this in a food processor.)

Add 1 tablespoon of water and continue mixing. Add more water as needed, 1 tablespoon at a time, until a dough forms.

Wrap the dough tightly in plastic wrap. Refrigerate for at least 2 hours.

Remove the dough from the refrigerator. If necessary, let it sit at room temperature for 10 to 15 minutes until slightly softened but still cold.

Lightly flour a work surface. Roll out the dough into a circle about 1/8-inch thick.

Transfer the dough to a 9-inch pie plate. Trim and crimp the edges as desired. Place the pie plate in the refrigerator while you make the filling.

Combine the brown sugar, flour, and salt. Add the milk and eggs, and mix well.

Stir in the Irish cream and vanilla.

Stir in the cooled butter and the chopped pecans.

Pour the mixture into the crust. Scatter the pecan halves over the top of the filling.

Place the pie plate on a lined, rimmed baking sheet to catch any potential spills. Bake 45-50 minutes, or until the top is puffed and set. The center should wobble just a bit when you gently shake the pan.

Place the pie on a wire rack to cool completely before serving.