Place a trivet in a large pressure cooker and cover it with water. Water should be about an inch or two above the trivet.
Place all ingredients for the orange custard in the jar of blender. I use the KitchenAid Artisan Blender. Whiz at high speed to blend.
Once blended, pour over the caramel. {You can starin it if you like}.
Tightly cover the tin with aluminium foil, and gently place on trivet in pressure cooker.
Turn on the heat, and cook WITHOUT WHISTLE, for 15-20 minutes. Allow to cool in pressure cooker.
Once cool, take out gently, and leave to chill, covered, for 4-6 hours, preferably overnight.
To serve, place a slightly deep or ridged flat plate/pie dish over the tin, and swiflty turn over. The caramel custard will release some liquid that the platter should have space to catch.
Top with fresh seasonal fruit, toasted walnuts etc. Serve chilled.