Preheat oven to 350°F.

In a heavy saucepan over medium heat, bring the maple syrup to a gentle boil.

Cook the maple syrup for 5 minutes, reducing heat if necessary.

Remove the saucepan from the heat.

Stir in the butter until melted.

Add the heavy cream and stir.

Transfer 1/2 cup of the mixture to a small bowl; whisk in the flour and salt and then whisk this back into the mixture in the saucepan.

Beat the eggs in a small bowl and then whisk them into the mixture in the saucepan until well incorporated and the consistency is smooth.

Roll out the pie dough and place it in a 9-inch pie plate. Pour the warm filling into the pie shell. (Add nuts to half or all of the pie at this stage if desired).

Bake in the oven for 50 - 60 minutes, until the center is golden brown, bubbly and relatively firm when lightly jiggled back and forth. Some jiggle is ok, but don't want too much.

Cool pie completely at room temperature before slicing. This will take at LEAST 1-2 hours.