Preheat lightly oiled outdoor grill or indoor grill pan, and cook pineapple wedges 3-8 minutes per side.
Puree grilled pineapple in food processor or high-powered blender until smooth, adding a splash of pineapple juice if needed.
Strain excess juice out of the puree.
Add puree, sugar, egg yolks, corn starch, and salt to small sauce pan. Bring to a very low simmer on medium heat, whisking constantly, until the mixture has thickened. It should coat a wooden spoon without dripping.
Remove from heat and whisk in the butter. Set aside to cool. (Can be made ahead.)
Spoon a small amount, about a tablespoon, of the grilled pineapple curd into each ramekin.
Preheat oven to 325°F.
Bring the cream to simmer in a medium sauce pan, but not to a full boil, and set aside.
In a medium bowl, whisk together the egg yolks, vanilla, and castor sugar until pale and creamy.
Add the hot milk to the egg mixture in a slow, steady stream while whisking to prevent curdling.
Return the mixture to the sauce pan and whisk 5-10 minutes over low heat to thicken.
Pour the mixture into the ramekins on top of the grilled pineapple curd, and place ramekins in a bain-marie: place ramekins in a cake pan or roasting pan. Fill the pan with warm water, about half way up the sides of the ramekins.
Bake until the creme brûlée is just set but still wobbly in the middle, about 35-40 minutes.
Remove the ramekins to the fridge to cool for at least 2 hours, and up to 3 days. Remove from fridge about an hour prior to serving.
When ready to serve, sprinkle a thing layer of castor sugar atop each creme brûlée, and lightly caramelize the sugar with a blow torch. Serve immediately.