Note: In a medium saucepan, combine 1 cup (250 mL) of the sugar and 1/4 cup (60 mL) water. Bring to a simmer over medium heat, stirring until sugar is dissolved. Increase heat to high and boil, without stirring, until syrup turns a deep caramel colour (watch carefully so it doesn’t burn). Remove from heat and, while whisking, carefully pour in 3/4 cup (180 mL) of the cream then half of vanilla extract; whisk until blended. Let cool. Grate tangerines to make 1-1/2 tsp (7 mL) zest; set aside. Squeeze juice from 3 tangerines; reserve. Cut off peel and white pith from remaining tangerines. Holding tangerine over a bowl, cut segments from between membranes. Strain juice from segments and add to reserved juice. Set segments and juice aside. Stir 1 cup (250 mL) of the caramel sauce and tangerine and lemon zest into Mascarpone cheese. In a chilled bowl, whip remaining cream to soft peaks. Beat in remaining sugar, vanilla extract and the cornstarch until firm peaks form. Layer half of the lady fingers in a 10- to 12-cup (2.5 to 3 L) clear glass bowl or serving dish. Drizzle with half of the reserved juice. Spread with half of the Mascarpone mixture; top with one-third of the tangerine segments then spread with half of whipped cream. Repeat layers ending with whipped cream. Cover and refrigerate for at least 4 hours or for up to 1 day. Cover and refrigerate remaining caramel sauce and tangerine segments separately. Just before serving, arrange remaining tangerine segments decoratively on top of tiramisu and drizzle with caramel sauce. Garnish with fresh mint.