Line a 9x9-inch pan with parchment paper, letting it hang over two opposite sides like handles.

Make the crust: To the bowl of a food processor fitted with a steel blade, add the pecans, oats, dates, coconut oil, and salt. Process in 10-second bursts, until everything is broken down and the mixture looks coarse and sticky. Grab a small amount and squeeze it in your hand—it should hold together easily. If not, add an additional 1 teaspoon coconut oil and repeat (the moisture of your dates will determine how much coconut oil you need).

Dump the crust into the baking dish and, with the back of a measuring cup, press it very firmly into an even layer, working it into the corners. Place in the refrigerator.

In a medium saucepan, whisk together the filling ingredients: pumpkin, coconut milk, sugar, maple syrup, cornstarch, vanilla, cinnamon, allspice, ginger, nutmeg, and salt.

Turn the heat to medium. Cook, whisking constantly (this is an arm workout! Embrace it). The mixture will first bubble gently, and when you stir, the bubbles will disappear. Then, the bubbles will get stronger. As soon as you can stir without the bubbles disappearing, start a timer. Continue cooking and stirring for 2 minutes more. The mixture will thicken and be harder to stir. This entire process will take 6 minutes or so.

Pour the hot filling over the chilled crust and smooth the top. Let it cool on the counter for 20 minutes, then cover and refrigerate at least 6 hours, or overnight.

Use the parchment paper to lift the bars onto a cutting board. Slice into bars of desired size. Top with whipped cream or whipped coconut cream as desired.