Preheat oven to 350 degrees F. Line 2 muffin tin with 24 paper liners. Set aside.
In a small bowl, mix together the graham cracker crumbs, brown sugar and melted butter until moistened. Drop a heaping Tablespoonful or so of graham cracker crumbs into the bottom of each muffin cavity. Gently compress the graham cracker crumb mixture into the bottom of the muffin cups. Bake for 5 minutes. Remove from oven, but keep the oven on.
Meanwhile, make the filling: In the bowl of a stand mixer, cream together the cream cheese and brown sugar until fluffy and light, about 1 minute. Add in the eggs, one at a time, beating well after each addition, followed by the pumpkin puree, vanilla extract, and pumpkin pie spice. Lastly, add in the sour cream and mix well, scraping the bottom and sides of the bowl as needed.
Using a cookie dough scoop, scoop out about 2 Tablespoons of pumpkin cheesecake batter into each muffin cup. Return to the oven and bake for 15-17 minutes or until the tops of the cheesecakes appear set and do not jiggle when gently shaken. Cool in the pans completely, then refrigerate for at least 2 hours to set before serving. Just before serving, garnish with freshly whipped cream and an additional sprinkle of pumpkin pie spice. Store any leftovers airtight in the fridge for up to 3 days.