To make the mandarin syrup, in a medium frying pan over medium heat, bring mandarin juice and sugar to a simmer, stirring until the sugar dissolves. Add the butter, 1 piece at a time, whisking until combined before adding more. Cook for 4 mins or until the mixture thickens. Keep warm.
In a large bowl, whisk the ricotta, egg yolks, two-thirds of the lemon rind, poppy seeds and a pinch of salt until combined. Whisk in the milk. Stir in the flour and baking powder. Whisk until just blended. In another large bowl, using an electric hand mixer, beat the egg whites and sugar until stiff peaks form. Using a large silicone spatula, in 2 batches, gently fold the egg whites through the ricotta mixture.
Melt 1 tsp butter in a large frying pan over medium-low heat. Ladle two ⅓-cup portions of the ricotta mixture into the pan. Cook for 2-3 mins each side or until pancakes puff, become golden brown around edges and are cooked through. Transfer to a plate and cover to keep warm. Repeat, in 4 more batches, with remaining butter and ricotta mixture.
Stir mandarin slices into the syrup. Top pancakes with mandarin syrup and remaining lemon rind. Serve with cream.