Cut off the top of the pumpkin and scrape out all the seeds and membrane (a large metal serving spoon works well) and then carefully cut it into sections with a paring knife.
Cut the skin off the flesh, then steam the flesh until tender, then puree in a food processor or blender until smooth.
Preheat barbecue to 425°F for indirect heating. Prepare pastry; set aside.
Combine brown sugar, sugar, flour, molasses, cinnamon, ginger, nutmeg, cloves and salt in bowl. Stir in pumpkin puree. Add eggs and heavy cream to the pumpkin mixture; mix well.
Pour filling into unbaked pie crust (see hint). Bake pie in the barbecue over indirect heat for 15 minutes; open vents or crack lid if using charcoal, or turn down burners if using gas, to lower temperature to 350°F and bake for 45 minutes longer, or until knife inserted in center comes out clean. Cool completely. Keep refrigerated.
Serve with a dollop of sweetened whipped cream, if desired.
Makes 8 servings.
Hint: To help prevent the pie crust from becoming soggy in a custard-style pie, carefully break one of the recipe's eggs into unbaked pie crust, swish it around to cover entire surface with egg white and then pour the egg out into your mixing bowl for the filling. Do NOT boil pumpkin - it will soak up the water and make a watery pie.