In your food processor's bowl, combine the sifted plain flour, icing sugar, and salt. Pulse for a few seconds to mix them. Add the very cold cubed butter and blend until you achieve very small crumbs of butter. Then, add the egg and mix until a rough dough begins to come together.

Bring the dough into a ball and place it between two large sheets of baking paper. Lightly flatten it with your hands, then use a rolling pin to roll it into a large disk about 3 to 4mm thick (1/6 to 1/8 inch). Place the rolled dough on a flat tray in the fridge to chill and rest for at least one hour, or overnight.

After chilling, remove the dough from the fridge and peel off the baking paper. Using a round cookie cutter, cut out disks of pastry that are slightly larger than the tartlet pans you are using. For example, if using mini tart pans that are 7 cm (1/4 inch) wide, cut out pastry disks that are about 10 to 12 cm (3/8 to 1/2 inch) wide.

Line the tartlet pans with the pastry, gently letting it fall down the sides of the pan. Press along the edges where the sides meet the bottom to ensure the pastry fits snugly. Pop the pans into the fridge to chill for at least 1 hour, or better yet, overnight. If you have leftover dough, roll it out again and chill for at least 2 hours to make more tartlet crusts.

Preheat your oven to 160 degrees Celsius / 325 degrees Fahrenheit. Prick the bottom of the pastry with a small fork. Cover each crust with a piece of crumpled baking paper, then fill with baking weights, dried beans, or rice.

Bake for 15 minutes. Take out the weights and baking paper, then bake for another 12 to 15 minutes. You'll know it's ready when the bottom feels dry to the touch and the edges turn a light golden color. Let it cool completely before moving on.

Take a medium to large heavy-bottom saucepan and add the caster sugar and water to it. Use a spatula to stir them together, making sure the water is evenly distributed.

Turn the heat to low and let the sugar melt slowly without stirring. You'll notice it begin to boil, forming large, clear bubbles.

Keep an eye on the sugar as it cooks. After about 5 to 10 minutes, you'll see its color change from white to orange to light brown, almost amber.

Slowly pour in room temperature or lukewarm cream into the saucepan. Be cautious as it will bubble vigorously and rise quickly. Take care to avoid getting burnt.

With a heat-proof spatula, vigorously stir the mixture until all the cream is fully incorporated, resulting in a smooth and shiny sauce.

Take the saucepan off the heat and allow the sauce to cool for 5 minutes. Stir in the butter until it's completely melted and mixed in, then add the sea salt and vanilla.

Pour the caramel filling into a clean jug or pastry bag, then carefully fill the tartlet crusts until they're about 2/3 full. Lightly tap the tarts on a hard surface to remove any air bubbles, then refrigerate them for 1 to 2 hours, or overnight, until they're set.

Dice the cooking chocolate finely (or use couverture chocolate callets/pistoles). Put them in a small heat-proof bowl and microwave for 30 seconds to a minute, or until the bottom of the chocolate starts to melt slightly.

Combine the cream and honey in a small saucepan. Heat over low heat until it begins to simmer. Pour this mixture over the partially melted chocolate and let it sit for 2 minutes.

Using a sturdy spatula, gently stir in a circular motion to blend the cream and chocolate. Keep stirring until the chocolate is completely melted and mixed with the cream, resulting in a smooth, glossy ganache.

Put the ganache into a pastry bag, then cut the tip to make a small opening and pipe it over the caramel layer. Lightly tap the tartlet on a hard surface and tilt it to help the ganache spread out evenly. Alternatively, you can drizzle the chocolate over the caramel for a different appearance.

If desired, top with a sprinkle of flaky sea salt and cocoa nibs.

Return the tartlets to the fridge to set for at least 1 hour, or up to 24 hours before serving.