Begin by making the maple cream sauce. It needs to chill before serving.
Pour the cream into a heavy saucepan. Add the maple syrup and corn syrup. Cook over a moderate heat, stirring constantly, until the sauce is thickened and reduced by about a third, about 20 minutes. Chill for at least an hour before serving over the warm peach crisp.
To prepare the peach crisp, preheat the oven to 350 degrees F. Butter a 9-inch square or 8- by 12-inch baking dish.
Start with the crumb mixture. In a medium bowl, combine the flour, brown sugar, granulated sugar, cinnamon, nutmeg and salt.
Cut the cold butter into pieces. Add the butter to the bowl and use a fork, pastry cutter or pastry blender to cut into the flour mixture. The mixture should resemble a moist, coarse meal.
Place the peaches in a bowl, add the lemon zest to the peaches, mix in the lemon juice and maple syrup and gently stir the peaches to combine. Pour the peaches into the prepared baking dish. Top with the crumb mixture, evening out the surface with a fork.
Cover tightly with foil and bake, about 15 minutes.
Remove the foil and bake until the topping is crisp and golden brown, about 30 minutes more. If the topping appears underdone, continue baking in 10 minute increments until it's done.
Spoon the warm crisp onto a plate, and drizzle the chilled maple cream sauce over the top.