In a medium bowl, whisk together the flour, sugar, and salt.

Cut in the cold butter until the mixture resembles coarse breadcrumbs.

In a separate small bowl, whisk the egg yolk, vanilla, and just 1 tablespoon of milk. Stir this into the dry ingredients.

Use your hands to work the dough a bit and to bring the dough together. The dough should be crumbly but cohesive when squeezed. It won’t form a ball or a loose ball like with pie dough.

I placed a piece of plastic wrap in a mixing bowl and then dumped the dough into there and wrapped it up into a very loose, crumbly disc.

Chill for 1 hour or up to 3 days.

Grease 4 non-stick mini tart pans with removable bottoms OR grease 9 cavities of a non-stick cupcake pan.

To make the tartlet plan tarts - place 90 grams of the dough in the pan. Press up the sides and evenly over the bottom of the pan. Do the same with the other pans.

To make cupcake pan tarts, use 40 grams of dough per cavity. Press it evenly up the sides and over the bottom.

Place the pans in the fridge for at least 45 minutes, freeze for 15 minutes, or cover and refrigerate for up to 3 days. If you’re chilling them for 45 minutes, you can go ahead and start with the filling recipe below. When you’re done with the filling, come back up here.

Towards the end of the chill time, preheat the oven to 375 °F (190 °C) and place a baking sheet large enough to fit the pans in the lower third of your oven.

After 45 minutes of chilling or 15 minutes or freezing, place the tartlets directly onto the hot baking sheet and bake.

Bake the cupcake pan tarts for 15-17 minutes or until golden around the edges, and the center bottom doesn’t look wet. That part won’t get browned. It’s fine if it cracks and puffs up a little. The tartlet pan tarts should be baked for 18-22 minutes, rotating halfway through if you notice them browning too quickly in certain areas until the sides are nicely browned and the bottom has browned a bit.

Remove the baking sheet and tartlets from the oven and place them on a wire rack to cool for at least 30 minutes or overnight.

In a medium saucepan over medium heat, add all the filling ingredients except the heavy cream and eggs.

When it starts to steam, stir frequently for about 5 minutes. This step removes some of the moisture, making the filling even creamier.

Remove from the heat, dump the filling into a bowl (that won't break when you dump something hot into it), and stir in the heavy cream.

Let it sit for 15 minutes or until no longer very hot (you don't want the eggs to scramble which will happen if it's too hot). If you have time, you can just let it sit for about 30 minutes and skip using an extra bowl.

Whisk in the eggs one at a time, just until combined. There should not be streaks of pure egg because you'll have baked eggs pieces in your piece. They need to be incorporated, but not beaten too much, because that'll cause cracks. The filling should be room temp or cold when added to the cooled, baked shells - not warm. About 20 minutes before you’re ready to bake to assembled tarts, preheat the oven to 300 °F (150 °C). Place the baking sheets back in the oven in the same position as for the crusts.

Pour 40 grams (or a little more) of pumpkin filling into each cooled cupcake tart crust and 82 grams (or a little more) of filling into each cooled mini tart pan crust. You’ll have some leftover.

Bake the mini tart pan tarts for 21-25 minutes and the cupcake tart pan tarts for 25-27 minutes. They won’t appear raw in the center of the surface and won’t appear liquid. When you tilt the pan, they’ll appear set. The filling will firm up as it cools, but won’t get totally firm. If you want to be exact, they should reach an internal temp of 175 °F (79 °C).

Let cool completely in the pans, about 1 hour, and then chill the tarts in their pans for at least 3 hours. This is needed to firm them up. You can also pop them in the freezer once they’re cool enough to not release a bunch of condensation. Once they’re thoroughly chilled, use a sharp knife to run along the edge of the cupcake pan tarts. They’ll come out easily. For the mini tart pan tarts, you can just easily remove the side and bottom pieces.

Pipe the whipped cream on top of the tarts and add a sprinkle of cinnamon.

Cover and refrigerate for up to 3 days.