Preheat your oven to 425°F. Spray a 12-cup muffin tin with non-stick spray.
Cut as many 5-inch circles (using a round cutter or a bowl or glass) as possible out of each pie crust and fit them into each tin, crimping over the sides as necessary. Reroll the scraps if needed to get 12 crusts.
In a bowl or a 4-cup glass measuring cup (I used the measuring cup to pour it into each muffin tin directly without dirtying another bowl), whisk together the pumpkin, pumpkin pie spice, sweetened condensed milk, eggs, and salt.
Pour the pumpkin mixture into each crust. Make sure not to fill to the top so that the pumpkin spills over the sides of the crust (if you’ve used a 5-inch cutter, you shouldn’t have that problem since the crust will be as tall as the muffin tin).
Bake at 425°F for 15 minutes, then lower the heat to 350°F and bake another 20-25 minutes until a knife inserted in the middle comes out clean (can also use a toothpick).
Let the pies cool in the pan for at least 30 minutes, then pop them out. Top with whipped cream and a sprinkle of cinnamon if desired.