Make the Pastries: In a small bowl, whisk the flour and salt together. Place the room-temperature butter in the bowl of an electric mixer, add the sugar, and beat until light and fluffy. Lightly beat the egg and add slowly to the butter-sugar mixture, mixing just until incorporated. Add the flour and mix with a spoon just until it forms a ball. Don’t overwork the dough or your crust will turn out tough. Flatten the dough into a disk, cover with plastic wrap and refrigerate for 45 minutes or until firm. Meanwhile, butter your tartlet pans or tart pan.

Remove dough from fridge and separate into 8 separate pieces (Please see note below if making one tart). If your dough is too hard, let it sit at room temperature for a few minutes. At this point, my dough was too sticky, so I covered the 8 pieces in plastic wrap and stuck them in the freezer for five minutes.

When the dough feels firm, roll out each piece of pastry on a lightly floured surface to fit the tart pans. Rotate the dough a quarter turn as you roll to help prevent sticking. (Rolling your dough between lightly floured sheets of parchment or wax paper will also help to prevent sticking.) Keep the remaining pieces of dough in the fridge while you roll out each pastry.

Carefully lay the rolled-out dough in the tart pan, pressing lightly along the bottom and up the sides and being careful not to pull on the pastry, which can cause it to shrink. Remove excess dough, saving to patch any holes that appear as you fit the dough into the pan.  Cover and freeze the tarts for 30 minutes.

Preheat oven to 375 degrees. When the oven is ready, remove the 8 unbaked tart shells and prick the bottom of the tarts with a fork. Place the tarts on a baking sheet in the center rack. Bake for 10 - 15 minutes or until the crust is dry and light golden brown. If the bottoms of the pastry shells puff up during baking, lightly press the pastries back down. Remove from oven and cool.

Note: To make one 8- or 9-inch tart, follow the instructions above but increase the baking time to 20-25 minutes.

Make The Caramel: In a medium saucepan, combine the sugar, water and corn syrup and bring to a boil. Boil over high heat until the caramel looks a medium-amber color, 5-10 minutes, and immediately remove from heat. Carefully whisk in the cream – the mixture will bubble up. Once it has settled, stir in the butter. Wait 10 minutes until the caramel has cooled slightly and add the salt. Stir and taste – if you like your caramel saltier add ¼ to ½ teaspoon more salt.  Set aside.

Begin Assembling The Tarts: Loosen the tart(s) from the pan(s) and set on a baking sheet. Pour the room temperature caramel evenly into the tart pans (or tart pan), leaving room at the top for a layer of ganache. Place tart(s) in the refrigerator for at least 30 minutes.

Make The Ganache: Meanwhile, heat the cream and butter in a small saucepan over medium heat. Place the chocolate chips or chopped chocolate in a medium-sized heatproof bowl. Set aside. Bring the cream mixture just to a boil, then immediately pour over the chocolate and allow to stand without stirring, with a plate on top of the bowl, for five minutes. Then stir gently, as you do not want to incorporate air into the ganache, with a spoon or whisk until smooth. If desired, add the liqueur.

Finish Assembling The Tarts: Once the caramel feels slightly firm on top, spoon 2-3 tablespoons of ganache on top of the caramel in the center of each tart and spread evenly to the edges. (If making one large tart, start with 1/2 cup ganache and add more as needed.) Place the tarts in the fridge for at least 15 minutes to set the ganache. The tarts can be stored in the fridge for several days, covered. Let them sit out at room temperature for approximately 15 minutes prior to serving.