Preheat your oven to 350°F (175°C). Line a 9 x 9 inch baking pan with parchment paper.

In a stand mixer, combine softened butter, brown sugar, and granulated sugar. Beat on medium speed for about 3 minutes until light and fluffy.

Add in one large egg and a splash of vanilla extract. Mix on low speed until combined.

Whisk together all-purpose flour and a pinch of salt in a separate bowl. Gradually incorporate this into the wet ingredients and mix on low speed until the dough just pulls away from the sides.

Press the dough evenly into the bottom of your lined baking pan. Bake for 15 minutes or until edges are lightly golden.

Combine pumpkin puree, heavy cream, remaining sugars, spices, and eggs in a bowl. Whisk until smooth.

Pour the filling over the hot crust, spreading it evenly.

Bake again at 400°F (200°C) for 15 minutes, then reduce to 350°F (175°C) for an additional 40 minutes.

Allow the bars to cool on a wire rack for about 45-60 minutes, then chill in the refrigerator for at least 3 hours.

Lift the bars out of the pan, slice into squares, and consider topping with whipped cream and a sprinkle of nutmeg.