To make the caramel, combine the maple syrup, coconut sugar, ginger powder, vanilla extract, and salt in a small saucepan. Cook the mixture over medium heat, stirring occasionally for 5-6 minutes, until it thickens slightly and becomes syrupy.
Pour the caramel into the bottom of six small ramekins, tilting them to evenly coat the base. Set aside.
In a saucepan over medium-high heat, whisk together the coconut milk, pumpkin, rum (if using), cinnamon, cardamom, nutmeg, cloves, sugar, and vanilla extract.
While the pot comes up to a gentle simmer, using the tines of a fork or a tiny whisk, mix together the agar agar powder, cornstarch, and plant-based milk in a cup or small bowl.
Once the contents of the saucepan have reached a simmer, gradually add the cornstarch slurry while continuing to stir the content of the pot for another 2 minutes, until the flan mixture is smooth and slightly thickened. Remove from heat.
Pour the flan base evenly into the prepared ramekins over the caramel layer. Refrigerate the flans for at least 3 hours, or until fully set.
To serve, unmold the flans by running a knife around the edges of each ramekin and inverting them onto plates. If some caramel sticks to the inside of the ramekin, use a spoon to scoop it out onto your plated flan.
Optionally, garnish with crushed gingersnap cookies and a sprinkle of cinnamon.