Grease a 13x9-inch baking dish and preheat the oven to 350°F.
Mix the finely chopped pecans with the butter, flour and brown sugar using your hands, until crumbly.
Press the mixture into the greased baking dish and cook in the oven for 15 minutes.
Let it cool completely.
Meanwhile, whisk the milk with the pudding mixes.
Stir in the powdered sugar, cream cheese and a cup of the Cool Whip until fully combined.
Spoon this mixture over the crust and top with the rest of the Cool Whip.
Sprinkle on the rest of the pecans, then chill until serving.