Using an immersion circulator, preheat a water bath to 185°F.
In a bowl, whisk together all ingredients except pie crust and whipped cream. Pour evenly between 5 quarter pint jars.
1 (15-ounce) can pumpkin puree, 1 (14-ounce) can sweetened condensed milk, 2 large eggs, 2 tsp pumpkin pie spice, 1/2 tsp salt
Mix the filling in a bowl or large measuring cup with a spout to make it easier to pour the mixture into the jars.
Screw lids onto jars until just fingertip tight. Drop into preheated water bath and cook for 1 hour.
Remove jars from water bath and let come to room temperature on the counter. Place in fridge for at least 2 hours.
Before serving, unroll pie crust onto a piece of parchament paper on a baking sheet. Bake according to package instructions, until just golden brown.
1 unbaked pie crust
To serve, top each jar of pie with whipped cream and a broken piece of pie crust.
1/2 cup whipped cream
Notes
Jars
Use smaller jars for smaller servings. I'd recommend quarter pint (4-ounce) jars being the largest you go. You do not need to adjust the cooking temperature or time if using smaller jars.
Make sure to only screw your jar lids on to fingertip tight, meaning only as tight as you can screw on with just your fingertips. You want to see air bubbles escaping when you drop the jars into the water! If you don't, the jars may break during cooking.
Gluten-free option
For gluten-free pies, omit the pie crust at the end or use your preferred gluten-free crust. You could also top the pies with gluten-free graham cracker crumbs.
Storage
Store cooled pies covered in the refrigerator for up to 3 days. Wait until just before serving to top with the pie crust pieces and whipped cream.