Sugar Syrup: Boil all ingredients in pan on high, remove from heat; let cool.
Pumpkin Gelato: Heat all ingredients in pan, stir in sugar syrup, heat to 140°F (60°C), cool to room temperature; chill overnight. Place in ice cream machine and freeze.
Pumpkin Filling: Heat all ingredients in pan to 122°F (50°C), let cool to room temperature, transfer to an airtight container; chill overnight.
Tart Crust: Preheat oven to 350°F (180°C). Grease 12 individual tart molds with nonstick spray. Roll out dough to ⅛ in (3 mm), cut and press dough gently into molds, bake 15-18 minutes or until set; cool to room temperature.
Crumble: Preheat oven to 350°F (180°C). Line a baking sheet with parchment paper. Roll out dough to ⅛ in (3 mm), transfer to baking sheet, bake until golden brown, let cool to room temperature; crumble.
Crème Chantilly: Whisk cream and vanilla bean seeds until medium stiff peaks form; transfer to a piping bag (star tip).
Plating: Spread filling into tart crusts, remove tarts from molds, pipe cream rosettes around edges, plate with crumble and gelato; garnish with garden cress.