Step 1: Toast the pecans. Preheat oven to 350°F (175°C). Spread pecan halves on a baking sheet and toast for 7-10 minutes, or until fragrant. Melt 1 tbsp butter and toss with toasted pecans. Set aside to cool.
Step 2: Prepare the pie crust. If using a frozen crust, follow package directions to pre-bake if necessary (often blind-baked for custard pies). If making homemade, par-bake according to your recipe until lightly golden. Let cool completely.
Step 3: Make the cream filling. In a medium saucepan, whisk together granulated sugar, cornstarch, and salt. In a separate bowl, whisk egg yolks until smooth. Gradually whisk in the milk into the egg yolks.
Step 4: Combine and cook. Slowly pour the egg yolk mixture into the sugar mixture in the saucepan, whisking constantly. Cook over medium heat, whisking frequently, until the mixture thickens and comes to a gentle boil. Boil gently for 1 minute, continuing to whisk.
Step 5: Finish the filling. Remove from heat. Stir in 1/4 cup unsalted butter and 2 tsp vanilla extract until fully melted and combined.
Step 6: Assemble the pie. Pour the hot cream filling into the cooled pie crust. Arrange the toasted pecan halves decoratively over the top of the filling.
Step 7: Chill. Cover loosely with plastic wrap (ensure it doesn't touch the pecans) and refrigerate for at least 4 hours, or preferably overnight, until thoroughly chilled and set.
Step 8: Prepare whipped topping (optional). In a cold bowl, whip heavy cream with powdered sugar and 1/2 tsp vanilla extract until stiff peaks form. Serve pie slices with a dollop of whipped cream, if desired.