Heat the milk, heavy cream, zest, cinnamon and fennel seeds. Steep for about 10 minutes.Whisk the eggs, egg yolks and sugar together in a bowl. Temper in the hot liquid. Strain through a fine sieve.Pour the custard into ramekins. Place ramekins on a baking tray. Bring the tray to a preheated 300F oven. Pour hot water in the baking tray about 1" high. Bake the pots de creme until set. Time will vary depending on the size of the ramekin.Let them cool and refrigerate them for up to 3 days. Seem to like them best at room temperature .