In a saucepan, combine all the crèmeux ingredients except the chocolate. Whisk to combine.

Remove from the heat and let it cool for 5 minutes. Then, add the chocolate and whisk until it melts, and the mixture becomes homogeneous.

Pass the mixture through a fine-mesh sieve into a bowl. Cover it with plastic wrap, ensuring it touches the chocolate crèmeux, and refrigerate for at least 4 hours or overnight.

Preheat the oven to 215F (100C) and line a baking sheet with parchment paper.

Add the salt, vanilla, and lemon juice. Whip, gradually increasing the speed from medium-low to high in a stand mixer fitted with a whisk attachment (or use a hand mixer) until stiff peaks form. The meringue should be shiny, thick, and hold its shape well. The whole process can take up to 15 minutes.

When done, sift in the cornstarch and fold it in with a rubber spatula.

Spoon out the meringue onto the parchment paper and shape it into a circle. Drizzle the melted chocolate on top of the meringue.

Using a toothpick or the tip of an offset spatula, swirl the chocolate into the meringue. Adjust the shape to your liking, but make sure the top is flat so you can pipe the cream on top later.

Place the baking sheet on the middle rack of the oven and bake for 2 hours. Then, turn off the oven, crack open the door, and let the meringues cool down to room temperature like that. The parchment paper should peel off the pavlovas easily.

When at room temperature, place the chocolate crèmeux into a piping bag fitted with a nozzle of your choice. Decorate the pavlova to your taste and serve.