Preheat oven to 350° F. Put ceramic ramekins (ideally should be between 3 1/2"-4 1/2" in diameter) into a roasting pan or other suitable dish (has to be taller than ramekins.) Add hot water until it reaches about 3/4 the way up the ramekins. Divide the custard between your ramekins filling about 3/4" deep.
Gradually pour the egg mixture into cream, stirring constantly. Add salt and vanilla. Strain custard (it will still be liquidy) into a container that is easy to pour out of, using a fine mesh strainer.
Mix (do not whip) the egg yolks, eggs, mandarin juice, and 112g of brown sugar until everything is nicely combined. Put cream into a saucepan, add mandarin zest, then over medium heat, warm cream to scalding point (stirring occasionally).