In a food processor fitted with the steel blade, mix together the flour, salt and baking powder. Add the butter and process 5 to 10 seconds, or until the dough is the size of small peas.

Add 4 tablespoons cold water and pulse 2 to 3 times. Watch the dough carefully and stop the machine as soon as the dough starts to clump together. It will look rough and lumpy and there may be pieces of butter. If it looks dry and crumbly, pinch the dough together with your fingers; if it holds together, it is done. If not, add more ice water (in the dry air in Denver, I usually need 7 or 8 tablespoons water). Do not allow the dough to form a ball on the machine blades, as then it will be overworked and tough.

Turn dough out onto a clean surface and form into 2 flat discs; wrap separately with plastic wrap and refrigerate for at least 30 minutes (up to overnight).

Preheat oven to 350 degrees. Generously butter a 12-cup muffin tin.

Take dough out of the refrigerator and let it sit at room temperature for around 20 minutes (this makes it easier to roll).

On a lightly floured work surface, roll dough to an even 1/8-inch thickness and into a square-ish shape. Cut out 12 (4 1/2-inch) circles - use a small bowl or a takeout container lid as a guide. You may have some leftover dough.

Fit the dough circles into the muffin cups, gently pressing on the dough so that it is snug in the muffin cups (I wear gloves so my nails don’t damage the dough). Refrigerate for 30 minutes.

Cut out 12 (4- to 5-inch) squares of foil. Line the dough in each muffin cup with a foil square and fill with pie weights. Bake for 20 to 30 minutes or until crusts are golden brown. Remove from oven. Remove foil and pie weights and let crusts cool in the pan for around 10 minutes, before removing to a wire rack to cool completely.

Using an electric mixer with the paddle attachment, cream together the butter, sugar, flour and salt. Slowly blend in eggs, then milk and vanilla. Place mixture in a heavy saucepan and cook over medium-low heat, whisking, until thick. Let cool 10 minutes.

Spoon filling into individual pie crusts and put on a parchment paper-lined cookie sheet. Refrigerate for at least 2 hours to set.

Pipe or spoon whipped cream onto top of pies. Sprinkle nuts over the top, if using.