Place the gelatin leaves in 2 cups of cold water and set aside.
Place the milk and lemon zest in a non-reactive pan over medium-high heat.
Place the almonds in a food processor, grind to a powder and pour into the heating milk. Bring the milk and almonds to a boil, remove from heat, cover and let stand 20 minutes.
Line a conical sieve with cheesecloth and strain the lemon zest and almond solids from the milk, pressing with the back of a spoon to remove all of the liquid. Set aside 1 1/2 cups of the flavored milk for the sauce and place the remaining milk, 1 1/2 cups sugar and the soaked gelatin leaves into a saucepan and bring just to a boil, stirring constantly.
Remove from the heat immediately and allow to cool to room temperature.
Grease the flan molds with the almond oil and set aside. Whip the cream to soft peaks and fold the cooled almond milk into the whipped cream. Spoon the almond milk mixture into the greased flan molds so that they're 90 percent full, and refrigerate at least 4 hours.
Meanwhile, crack the eggs and beat together the egg and the yolks.
Add the egg mixture to the remaining 1 1/2 cup flavored milk, and add the remaining 1/2 cup sugar.
Place over medium heat and, stirring constantly, heat to a high simmer, 175 F.
Remove from heat, pour through a strainer into a small bowl and refrigerate 1 hour. To serve, dip the molds upright into a bowl of hot water, without allowing any water to go over the edge into the mold, and carefully invert onto a large plate.
Whisk the sauce to loosen it and pour over the custards into the plate.
