Preheat oven to 350°F. Generously grease twelve 4-ounce ramekins with non-stick cooking spray, place on a baking sheet, and set aside.

In a mixing bowl, combine the butter, brown sugar, corn syrup, and vanilla until well combined. Add about 2 teaspoons of the mixture to the bottom of each ramekin and lightly press it down. Add about 2 Tablespoons of pecans to each ramekin, spreading them out to cover the entire bottom. Set aside.

In the bowl of a stand mixer fitted with a paddle attachment, cream the butter and sugars until fluffy and light in color, about 3 minutes. Add the eggs one at a time and vanilla, combining well after each addition. Scrape the bowl and mix on high for another 20-30 seconds until smooth.

In another bowl, combine the flour, cinnamon, baking powder, baking soda, and salt. Add half of the flour mixture and the pumpkin puree to the bowl and mix just until combined. Scrape the bowl and add the remaining flour. With the mixer on low speed, slowly stream in the buttermilk. Scrape the bowl and mix one final time on medium-high speed for about 10 seconds.

Divide the batter evenly between the prepared ramekins, filling them about ¾ full. Bake for 30-32 minutes, or until the center springs back to the touch or a toothpick inserted comes out clean.

In the bowl of a stand mixer fitted with a whisk attachment, whip the heavy cream, powdered sugar, and cinnamon until medium peaks form. Store in the fridge until ready to serve.

Allow the cakes to cool for 10 minutes. Run a spatula around the edge of each ramekin to loosen the cake, then carefully flip each one onto a baking sheet lined with parchment paper. Tap the ramekins to help release the cakes. Lift the ramekins off and scoop out any extra pecan topping, adding it to the tops of the cakes.

Serve the cakes warm or at room temperature, with a dollop of the cinnamon whipped cream.