Preheat your oven to 350°F (175°C) and grease a 9x9 inch cake pan. In a mixing bowl, whisk together the all-purpose flour, baking powder, baking soda, salt, cinnamon, and pumpkin pie spice for a well-blended dry mix. In a separate bowl, combine the granulated sugar, pumpkin puree, vegetable oil, whole milk, and eggs, mixing until smooth. Gently fold the wet ingredients into the dry until combined, then pour the batter into the prepared pan. Bake for 20-25 minutes, or until a toothpick inserted in the center comes out clean. Allow the cake to cool completely before cutting it into small squares.

In a medium saucepan over medium heat, combine the salted butter, brown sugar, and heavy whipping cream. Stir constantly until the mixture starts to boil, then let it simmer without stirring for about 1 minute. Remove the saucepan from heat and stir in the vanilla extract. Allow the caramel sauce to cool for a bit before transferring it to a jar or container for later use.

Preheat your oven again to 350°F (175°C) if it's not already. Spread the pecan pieces in a single layer on a baking sheet lined with parchment paper. Toast the pecans in the oven for about 7 minutes, stirring occasionally, until they're fragrant and lightly browned.

In a large mixing bowl, beat the cream cheese with sugar until it’s smooth and creamy. Gradually add the heavy whipping cream while continuing to beat the mixture until thick, forming stiff peaks. Gently fold in the vanilla extract.

Layer your Mini Caramel Pecan Pumpkin Cheesecake Trifles by adding a spoonful of caramel sauce at the bottom of each clear cup. Next, add a layer of pumpkin cake squares, followed by a layer of cheesecake filling. Sprinkle some toasted pecan pieces on top, then repeat the layers until the cups are nearly full. Finish each trifle with a final drizzle of caramel sauce and garnish with whole pecan halves.