*Or, 2 orange zest and a few drops orange extract. A day before, place mandarine in a saucepan and cover with water – bring to boil and cook for 2 minutes. Cover, turn off the heat and let sit overnight. Drain mandarine and rinse. Quater and remove any white membranes and seeds. In a food processor, blend sugar with the diced candied orange peels. Add the chopped mandarine and give a few pulses to puree. Transfer mandarine mixture into a saucepan or frying pan, add grapefruit juice, bring to boil and cook for 20 min on medium low heat stirring every so often and cool. Keep refrigerated for up to 3 weeks.
In a food processor, lightly toast and blend 120g pistachio with a drizzle of vegetable or pistachio oil. Add a couple drops of almond extract – process to paste. Store for months in the refrigerator.
Sift flour with baking powder; set aside. In a large pastry bowl, combine together zests, eggs, salt, sugar, pistachio paste (30g) and the cubed almond paste. Heat up to 122ºF/50ºC whisking constantly over water-bath (Hot water must not touch the bottom of the pastry bowl). Transfer warm mixture in the mixing bowl and beat on high speed until fluffy and cool; it should take 10 minutes. In a separate bowl, mix one-third of the mixture with the melted butter – add remaining batter and fold in the sifted powder.
Turn oven on to 400ºF/200ºC. Spread batter onto a large baking tray lined with a lightly oiled silicone mat or parchment. Bake pain de gênes for 8 min – cool completely.
Soak gelatin in cold water for about 10 min. Drain well. In a large saucepan, gather all ingredients but the gelatin. Bring to a quick boil whisking constantly. Transfer lemon custard in a separate pastry bowl and mix in soften gelatin. Cool on ice water and chill. Save 7oz/200g lemon custard for the lemon chantilly and save remaining lemon custard for the topping.
Smooth out lemon custard and fold in whipped cream; refrigerate.
Line baking pan with plastic wrap (lightly coat the mold with some oil so then the plastic film wont move). Make 2 equal pain de gêne squares which would fit into the baking pan. Place the first pain de gênes sheet (skin side up) in the pan. Spread evenly 400g citrus marmalade. Enclose with the second pain de gênes sheet (skin side down). Cover the surface with small lemon custard balls followed by the lemon chantilly. Freeze the cake to set. Unmold and split in half; cut each half into 5 bars (10 servings). Let thaw and garnish with mandarine supremes and poached lemon if desired. Enjoy!