Preheat oven to 350 degrees F. Grease a 9x9 inch pan.
In a large bowl, mix flour, baking powder, baking soda, salt, cinnamon, and pumpkin pie spice.
In another bowl, beat sugar, pumpkin, oil, milk, and eggs together. Mix in the dry ingredients until combined and then pour into the greased pan. Bake for 20-25 minutes until toothpick comes out clean.
Let cake cool completely. Cut into bite size squares when cooled.
For the Brown Sugar Caramel Sauce:
Heat butter, brown sugar, and whipping cream in a 2 quart pot over medium heat, gently stirring with a wooden spoon or heat resistant spatula. Once it comes to a boil, cook for 1 minute. Remove from heat, stir in vanilla and let cool slightly before pouring into a jar. Store in fridge until ready to use.
For the Nuts:
Place pecans on a baking sheet and bake at 350 degrees for 7 minutes. Remove from oven and let cool.
For the Cheesecake Filling:
Beat cream cheese and sugar together until smooth. Add the whipping cream and vanilla and beat until stiff peaks form. Place in a piping bag for assembling the trifles.
For Assembling the Trifles:
Pour about a teaspoon of caramel into the bottom of each dish/cup. Add a layer of cubed pumpkin cake followed by a layer of filling. Sprinkle on about a tablespoon of pecan pieces and then drizzle with more caramel.
Repeat the layers until you get to the top of your dish/cup. End with a drizzle of caramel and pecan halves.
Serve immediately or if making in advance, wait to assemble until at most an hour before serving.