Prepare the Pastry:

1. Add the flour, powdered sugar, cocoa powder, and salt to the bowl of a food processor.
2. Pulse until combined.
3. Add in the butter and pulse 7 times.
4. With the motor running, add in the egg and let process until a dough forms together into a cohesive ball.
5. Scrape the dough from the bowl onto a piece of plastic wrap. Form the dough into a disk and wrap it tightly.
6. Using a rolling pin, roll the dough out until it stretches to the edges of the plastic wrap to ensure a tight seal.
7. Refrigerate for at least 2 hours, but preferably overnight.
8. Roll out the pastry on a lightly floured surface to ⅛ to ¼-inch thickness. Using a circle cutter 1-½ inches larger than the diameter of your mini tartlet pans, cut out rounds of dough. (See note about mini tart pans.)
9. Place the circles of pastry in the tins, taking care to press the pastry into the sides and the bottom. Chill the mini tart shells in the refrigerator for 15 minutes.
10. Meanwhile, preheat the oven to 375ºF and place an oven rack in the lower middle part of the oven.
11. Once chilled, line each tart shell with a small round piece of parchment paper or a muffin liner, then add pie weights (I recommend dry rice or beans or lentils), making sure to push the pie weights to the edges.
12. Bake on the lower-middle rack for 12 minutes, then remove from the oven and carefully remove the parchment and pie weights. Return to the oven and bake the tartlets for an additional 5-8 minutes, or until the pastry is fully cooked through. Set aside to cool completely until ready to use. This can be done up to one day ahead of time.

Make the Fillings:

1. In a medium pot, combine the granulated sugar, lemon juice and half of the prepared strawberries. Cook over medium heat, stirring frequently, until the strawberries have reduced by half and thickened, 8 to 10 minutes, mashing the berries with a potato masher or a fork halfway through cooking. Transfer to a container and let cool.
2. In a small pot, heat the cream over medium-low heat until it’s bubbling around the edges. Add in the chocolate and salt and stir together until the chocolate starts to melt. Shut off the heat and continue to stir until the chocolate is fully melted and the ganache is glossy. It will be very thick. Set aside until ready to use.

Assemble:

1. Spoon a heaping tablespoon of the cooked strawberries into the bottom of each fully-baked tartlet shell.
2. Slice one of the remaining raw strawberries horizontally while keeping the shape of the strawberry intact. Gently push down to fan out the pieces, then place in one of the tartlets. Repeat with remaining strawberries and tartlets. Depending on the size of the tarts made, they can each fit 1-2 strawberries.
3. Generously drizzle the prepared chocolate ganache on top of the strawberries. The tarts can be served immediately, or they can chill in the refrigerator before serving. They should be served the same day they are made.