Put the orange juice, zest and sugar into a pot and simmer on low till nice and syrupy or reduced by 1/2. Pour into a jug and set aside.
Put the yolks, buttermilk, zest and sugar into a bowl and whisk till combined. Mix the cinnamon, baking powder and flour together and whisk gently into the egg yolk mixture. The mixture should be stirable. If it is too thick and a little more buttermilk.
In a clean bowl, with a clean whisk beat the whites to soft peak and nice and fluffy then fold through the batter along with the chopped walnuts till just incorporated without mixing too much.
Heat a fry pan greasing with a little butter testing with a small drop of the batter. Once hot reduce the heat a little and add the first quarter of the batter. The pancakes with be very fluffy. Turn when they start to bubble on the top. Cook slowly so the outside doesn't burn. keep warm wrapped in a clean teatowel till all are finished
Once all four are done layer with the mascarpone. and decorate with fruit and more mascarpone and nuts. Serve with lashings of the syrup and extra cream. Cut just like a cake.