First, make the maple caramel. In a small, heavy-duty saucepan fitted with a candy thermometer, combine sugar, maple syrup, and water. Cook over medium heat without stirring, but feel free to gently swirl the pan to combine the ingredients. Keep an eye on the thermometer; it's ready when it reaches 230ºF (110ºC).
As soon as it hits the right temperature, immediately remove the saucepan from the heat. Quickly sprinkle in flaky sea salt and pour the caramel into an 8-inch (20cm) cake pan. Make sure it has sides at least 2 inches (5cm) high. Let it cool until room temperature, about 30 minutes.
While your caramel sets, preheat your oven to 350ºF (180ºC). This way, your flan will bake perfectly once you pour in the custard.
In a stand mixer or using a sturdy whisk in a medium-sized bowl, mix together the sweetened condensed milk, evaporated milk, pumpkin puree, and mascarpone until smooth. You want it to be creamy and well combined, so don’t rush this step!
Next, whisk in the eggs, vanilla extract, ground cinnamon, ground allspice, and orange zest. Keep mixing until everything is fully blended. The mixture should be silky and aromatic.
Now, carefully place the caramelized cake pan into a roasting pan. To avoid disturbing your beautiful caramel, pour the custard over the back of a large spoon or spatula into the cake pan.
Once you’ve added the custard, add very hot tap water to the roasting pan, filling it so that the water reaches halfway up the outside of the cake pan. This hot water bath will help the flan cook evenly.
Place the whole setup on the middle rack of your oven and bake until just barely set, about 70 to 75 minutes. The center should be slightly jiggly, but the edges will be firm and set.
After baking, remove the flan from the water bath and let it cool completely on a wire rack. Then chill it in the refrigerator for 3 to 4 hours, or overnight if you can manage the wait!
Finally, when you’re ready to serve, run a sharp knife around the outside of the flan to release it from the sides of the cake pan. Place a serving platter upside down on top of the flan.
With both hands, flip the flan and the platter over simultaneously. Hold both the cake pan and platter, then gently shake to release the flan. If it doesn’t come out easily, slide your finger along one edge to break the airlock. Let it fall out gently to keep it intact.
