Preheat the oven to 200°F and place the rack in the middle of the oven.
Line a half sheet baking sheet with parchment paper. Use a pencil to outline a 9” x 12” rectangle on the parchment to serve as a guide. (A ¼ sheet baking pan serves as an excellent template.) Turn the parchment paper over so the pencil line will touch the baking sheet and not the meringue.
In the bowl of a stand mixer fitted with the whisk attachment, place the egg whites, salt, and cream of tartar. Beat on medium speed until frothy. Slowly add the sugar to the egg whites, one tablespoon at a time. Add the vinegar and vanilla. Continue mixing on medium, whipping until the whites are glossy and thick, like marshmallow; this will take about 8 minutes.
Turn off the mixer and remove the bowl and whisk. Use a fine mesh strainer to sift the cornstarch and cardamom over the meringue. Gently fold the cornstarch and cardamom into the meringue using a rubber spatula. Fold in the desiccated coconut.
If you have a pastry bag and a large piping tip, you can pipe the meringue onto your parchment lined baking sheet. (I like to pipe swirls, or ‘kisses’ in rows of 5 by 8.) Alternatively, you can transfer the meringue to the baking sheet using a rubber spatula then use an offset spatula to evenly spread the meringue within your pencil drawn rectangle.
Bake the meringue in the preheated oven for 1½ hours. Turn off the oven and leave the meringue in the oven with the door cracked slightly (use a wooden spoon) to cool completely, at least 1 hour, possibly longer. Remove to a cooling rack. If serving within a few hours, the meringue can sit out. If serving the meringue later, it’s a good idea to carefully wrap the meringue in plastic wrap.
Coconut custard & whipped cream
Place the milk and coconut milk in a heavy saucepan, and bring to a simmer over medium heat. Do not let the milk come to a boil.
In a medium bowl, whisk together the cornstarch, sugar, and salt. Add the egg yolks and whole egg to the dry ingredients, whisking until smooth and well blended. Gradually add a few tablespoons of the warmed milk to the egg mixture, whisking until smooth. Whisk in a few more tablespoons of milk, to temper the eggs. Slowly add the remaining warm milk to the egg mixture, whisking constantly, then transfer the egg/milk mixture back to the saucepan.
Cook over low heat until the mixture thickens and begins to sputter; you should see a few large bubbles, but don’t let it boil. Allow the custard to cook for an additional 2 minutes then remove the saucepan from the heat. Add the butter and the vanilla, whisking until smooth. Pour the custard through a fine mesh strainer set over a bowl.
Fold in the coconut and cover the custard with a piece of plastic wrap to prevent a skin from forming. Transfer the custard to the refrigerator to cool completely. The custard will keep in the refrigerator for up to 3 days. Prior to serving, prepare the whipped cream.
Using a handheld mixer or a stand mixer fitted with the whisk attachment, whip the cream with the sugar in a chilled bowl, until soft peaks form. Add the vanilla. Cover and refrigerate until ready to use.
To assemble the pavlova, place the meringue on a large serving platter. Use an offset spatula to spread the cold custard over the meringue. Dust the pavlova with coconut to garnish. Serve with fresh strawberries and whipped cream. (Note: I find the meringue cuts into neat squares using a sharp knife and wiping the knife clean between cuts.) Cover and refrigerate any leftovers.