Combine the water and sugar in small saucepan on medium heat. Once the sugar has completely dissolved, add the pumpkin puree, cinnamon, ginger, nutmeg, and allspice and boil for 5 minutes, stirring frequently. Remove from heat and allow to cool completely.
For the Pumpkin Spice Marshmallows
In a stand mixer bowl with whisk attachment, add 1/2 cup water and sprinkle the gelatin over the water. Allow to sit to fully absorb the water.
In a medium saucepan over high heat combine the sugar, 1/2 cup water, light corn syrup, and salt. Bring to a rolling boil and allow to boil for one minute, stirring constantly.
Turn the mixer on to low and let is mix the gelatin a couple times before slowly adding the hot sugar mixture. Once completely incorporated, turn the mixer up to medium-high and allow to beat for about 7-10 minutes, or until the mixture has doubled in size and is white and fluffy, scraping the sides frequently to keep it from spilling over.
Pour the mixture into a buttered 9x13 pan, then drizzle with the pumpkin spice syrup and drag a knife through it in both horizontal and vertical strokes to create a marbled appearance. Allow to sit, uncovered, for a minimum of 4 hours, or for best results, overnight. Dust with powdered sugar and slice with a buttered knife.
For the Pumpkin Spice Latte
In a large coffee mug, add the pumpkin spice syrup, followed by the fresh black coffee. Slowly mix in the hot milk and top with milk froth and diced marshmallow cubes. Enjoy!