Prep pumpkin and dice. Steam for 10 minutes and purée. In a bowl, whisk sugar, egg yolks and orange juice. In a saucepan, bring milk and mascarpone to a boil. Pour over step 2 preparation, mix actively and put back over medium heat. Thicken while continuing to stir. Add pumpkin purée, grated coconut, mix well and let cool. Assemble tiramisu alternating cream and brownie pieces layers.