Prepare a crumb base mixing crumbs with the brown butter until it resembles wet sand.
Line a 9x13-inch (23x33cm) pan with 2-inch sides with aluminum foil, letting it hang over the two long sides (the short sides won’t have foil). Pat the crumb mixture evenly over the bottom. Refrigerate while making the filling.
Beat the cold cream in a medium bowl until medium peaks form when the beaters are lifted. The tip will fall slightly and the cream will have some consistency but not be completely firm.
Beat cream cheese until smooth in a large bowl.
Add the half whipped cream and beat until beginning to thicken about 1-2 minutes. The peaks when you lift the beaters should be quite firm but with a slight drop.
Stir in the condensed milk, lemon zest, and vanilla, and mix well.
Pour the cheesecake mixture over the prepared base.
Add dollops of passionfruit curd all over the batter, using about 1 ½ cups of the curd mixture. With a smooth-bladed knife, swirl it lightly.
Refrigerate for 2 hours, or until it's firm enough to cut. Or freeze it, well covered in plastic wrap first, and then aluminum foil.
Serve cold. Take out of the freeze about 15 minutes before serving. Cut into squares and serve.