Preheat oven. Cut thawed puff pastry sheet into 6-8 pieces. Pierce each a few times with a fork or sharp knife. Bake according to package instructions, removing when golden, crispy and cooked all the way through. Set aside to cool. Do not turn off oven- set to 400 degrees Fahrenheit. Prepare your milk mixture- combine whole milk, 1/4 cup heavy cream, sweetened condensed milk, vanilla, and cardamom or cinnamon, if using, in a small pot. Set on stove over medium heat, stirring occasionally to ensure milks are fully combined. Be careful to not let the milk scorch in the bottom of the pot.
Whip remaining 3/4 cups of heavy cream together with confectioners sugar, either by hand with a whisk, or in the bowl of a stand mixer, until medium peaks form. Place in fridge.
Once cool enough to handle, cut pastry into 1-2 inch pieces and place in a pie pan or 9x13 inch baking pan.
Sprinkle any desired nuts, coconut, raisins or chopped dried fruit over the pastry pieces. Mix the pastry around slightly to allow the mix-ins to distribute throughout.
Pour the hot milk over the pastry. Allow to sit for 10 minutes so the pastry can soak up the milk.
Dot the surface of the pastry with whipped cream topping,, then spread it all over the top using a spatula or back of a spoon.
Bake the om ali on the middle rack of your preheated oven at 400F for 15 minutes.
Switch the oven to broil function, keeping the om ali on the middle rack and no closer to the broiler. Broil, watching carefully, until golden brown with some darker spots, 2-3 minutes.
Let rest 10 minutes before serving.
Serve hot with nuts, coconut, raisins and chopped dried fruit for topping, as desired.