Prepare the Pastry:

1. Whisk the flour, salt and sugar together in a large bowl. Add the cubed butter and, using your fingertips, lightly rub the butter into the flour until it resembles large breadcrumbs with some pieces the size of small peas. You can also use a pastry blender for this job.
2. Make a well in the middle of the flour mix and add the egg. Using a wooden spoon, mix the egg into the flour until they are completely combined.
3. Add the cream and mix until the dough is firm enough to form a ball when you press the mixture together with your fingers—it might be a little crumbly, but form the dough into a disk and wrap it tightly in plastic wrap.
4. Refrigerate for a minimum of 1 hour, or up to 3 days, in the fridge. You can also freeze the dough, tightly wrapped in plastic, for up to 3 months. Thaw it overnight in the fridge before you roll and bake.

Assemble and Bake the Tarts:

1. Remove the disk of dough from the fridge and let it sit for a few minutes so it’s easier to work with. Cut the dough in half.
2. Lightly flour a large sheet of parchment, then place one piece of dough on the parchment. Sprinkle it lightly with flour and place a second sheet of parchment paper on top.
3. Roll the dough between the two sheets of parchment paper to a thickness of 1/6 inch (4 mm). If the dough is soft, you might need to put it back in the fridge to firm up a little before you cut it.
4. Preheat the oven to 375˚F (190˚F). Lightly grease two 12-cup muffin pans with butter.
5. Using a cookie cutter that’s about 3 inches (8 cm) in diameter, cut out rounds of the dough. A cookie cutter with fluted edges makes for pretty tartlets but if you don’t have a cookie cutter, you can use a glass or ramekin that’s the same diameter. One disk of the pastry should make ten rounds. You will need to gather up and re-roll scraps of the pastry to make sure you get ten—and each time you re-roll, you will need a touch of flour to ensure the pastry does not stick to the parchment. You may need to refrigerate the dough again once it’s been rolled out if it is very soft and sticky.
6. Use an offset spatula to help you remove the pastry rounds from the parchment and gently place them in the muffin cups. You don’t need to press them right down to the bottom, as gravity will help them sink to form a little cup. Make sure the pastry rounds are evenly centered in the muffin cups. Place the muffin pan in the fridge while you work with the second piece of dough.
7. Repeat with the second piece of dough and refrigerate the muffin pan and pastry rounds for 30 minutes.
8. Place 1 teaspoon of jam in the middle of each pastry round. It doesn’t look like a lot but it will bubble up and expand when it cooks.
9. Bake for 20 minutes, until the pastry is golden and the jam is bubbling.
10. Remove the pans from the oven and let the tarts sit in the pans for about 15 minutes, or until the jam is no longer runny. Remove the tartlets from the pans and cool on wire racks. Serve at room temperature. You can store these in an airtight container for up to 3 days—they will get soggy the longer you store them, though, so best to eat them up!