Cream ½ cup of softened butter with ½ cup of granulated sugar until light and fluffy. Beat in one egg yolk and a teaspoon of vanilla extract. Gradually mix in 1 cup of all-purpose flour, 1 cup of oats, and a pinch of salt until a soft dough forms. Cover and refrigerate for at least 30 minutes.

Preheat your oven to 375°F (190°C). Press the chilled dough into a 9-inch pie plate. Chill again for 10-15 minutes. Bake for 12-15 minutes until golden brown; set aside to cool.

Combine 1 cup of whole milk and 1 cup of heavy cream in a saucepan over medium heat until small bubbles form at the edges. Remove from heat and allow to cool slightly.

In a large bowl, whisk together 4 large eggs, ¾ cup of granulated sugar, 1 teaspoon of vanilla extract, and the selected spices until pale yellow.

Slowly pour the warm milk mixture into the egg mixture while whisking continuously to combine.

Strain the mixture through a fine sieve into another bowl to ensure a smooth filling. Pour evenly into the pre-baked crust.

Bake in a preheated oven at 325°F (163°C) for 45-60 minutes until the edges are set and the center jiggles slightly.

Let the pie cool at room temperature for about 2 hours, then cover and refrigerate for at least 4 hours before serving.