Step 1: Preheat oven to 375°F (190°C). Prepare your pie crust by fitting it into a 9-inch pie plate. Crimp the edges decoratively. Blind bake the crust by lining it with parchment paper, filling with pie weights or dried beans, and baking for 15-20 minutes, or until edges are lightly golden. Remove weights and parchment and bake for an additional 5-7 minutes, until the bottom is lightly golden and dry. Reduce oven temperature to 325°F (160°C).
Step 2: In a large bowl, whisk together the eggs, granulated sugar, and salt until well combined and slightly frothy.
Step 3: In a medium saucepan, gently heat the whole milk, heavy cream, and 1 teaspoon of ground cinnamon over medium heat until small bubbles form around the edges and the mixture is steaming, but not boiling. Remove from heat.
Step 4: Slowly temper the egg mixture by gradually whisking about half of the warm milk mixture into the eggs. This prevents the eggs from scrambling. Then, pour the tempered egg mixture back into the saucepan with the remaining warm milk, whisking constantly until smooth.
Step 5: Stir in the vanilla extract. For an extra smooth custard, strain the entire mixture through a fine-mesh sieve into a clean bowl.
Step 6: Carefully pour the custard filling into the blind-baked pie crust. Place the pie on a baking sheet to catch any potential spills and bake for 50-60 minutes, or until the edges are set and the center has a slight jiggle when gently shaken.
Step 7: Remove the pie from the oven and let it cool completely on a wire rack for at least 2-3 hours. For best results and optimal setting, refrigerate for at least 4 hours, or preferably overnight, before slicing and serving. Dust with extra cinnamon before serving, if desired.