1.
Set rack in the middle of the oven and preheat oven to 190 C / Gas 5. Lightly oil a 23cm quiche dish. Set aside.
2.
Spread nuts over a baking tin. Toast for 7 to 10 minutes or until the smell of nuts fills the kitchen. Set aside 16 pecan halves for garnish.
3.
Combine oats, flour, remaining pecans, 1/2 teaspoon cinnamon and a pinch of salt into a food processor. Pulse until mixture becomes coarsely ground. Transfer to a mixing bowl. Whisk together oil and 3 tablespoons maple syrup and mix into dry ingredients to form a soft dough. Press mixture into prepared quiche dish. Crimp edges. Bake for 10 minutes and set aside to cool.
4.
Blend soya milk and arrowroot in the food processor until the arrowroot is completely dissolved and the mixture is smooth, about 15 seconds. Add pumpkin, maple syrup, ginger, 1 1/2 teaspoons cinnamon, 1/2 teaspoon salt, nutmeg and cloves; process until thoroughly blended. Pour filling into baked base and smooth the top with a spatula.
5.
Bake for about 35 minutes or until the base is lightly browned and the outside 2.5cm of the filling is set. Don't worry if the centre is still soft; it firms up as the pie cools. Transfer pie to a wire the rack. Gently press toasted pecan halves into hot filling in 2 concentric circles. Cool to room temperature and then chill until set, about 3 hours. Serve chilled or at room temperature.