Put ice 4 or 5 ice cubes in a measuring cup and fill with cold water.
In a food processor, put 2 cups all-purpose flour, 6 tablespoons unsalted butter and pinch salt. If making it by hand, use a large bowl and a dough cutter or your hands to integrate the butter and shortening.
Add 6 tablespoons unsalted butter and 4 tablespoons shortening, cold and in pieces and pulse using on/off turns until the butter and shortening are the size of peas or beans. It will be irregular.
Add about ½ cup ice water and pulse a few times.
Check the bottom of the bowl with a spatula so that you don't have a lump of flour that the blades didn't pick up.
Check if the mixture is too dry and floury. If you take some and squeeze it in your hand it should hold its shape and not crumble apart.
Add more water (a teaspoon at a time if needed) and pulse until it barely comes together. Check the dough again. If you take some and squeeze it in your hand, it should hold together and not crumble.
Transfer dough to a barely floured surface and gather it together into a ball.
Don't overwork it or the dough will be tough.
Wrap in plastic and refrigerate for an hour or up to 3 days. Or freeze for up to a month.