Make the Pumpkin Spice Sauce - In a medium saucepan add the granulated sugar and water. Bring to a simmer over medium-low heating, stirring until the sugar has dissolved.Add the cinnamon sticks, pumpkin puree, nutmeg, cloves, and ginger, and stir to combine. Reduce heat to low, and simmer until the syrup is fragrant, about 20 minutes. Do not let the mixture bubble, gently infuse the spices into the syrup.
Strain the Sauce - Pour the syrup through a cheesecloth-lined sieve or fine-meshed strainer. Lightly press the mixture through to extract the spice flavor. Use pumpkin spice sauce in the latte as directed. For the leftover syrup, cool to room temperature. Transfer to a glass container, cover, and refrigerate.
Heat the Milk - Warm the milk over medium-low heat on the stovetop until hot, between 140 to 145ºF (60 to 63ºC). Alternatively, microwave in 15-second intervals until the desired temperature is reached. Use a frother if desired to make foam.
Make the Latte - Depending on the desired sweetness, add 1 to 4 tablespoons of the pumpkin spice sauce to a 10 to 12-ounce coffee cup. Add the espresso and stir to combine. Add the hot milk, then if desired, top with foam.
Make the Whipped Cream (Optional) - In a medium bowl, whisk the heavy whipping cream until medium peaks form.
To Serve - Top the latte with whipped cream (if using) and a sprinkle of pumpkin pie spice. Enjoy!
Notes
Pumpkin Spice Sauce Yield: About 2 cups, use 1 to 4 tablespoons per latte. Makes around 16 servings.
Storing Sauce: Let the syrup cool to room temperature. Transfer to a glass container with a lid. Store for up 2 weeks in the refrigerator.
Stronger Latte: Add about 1.5 to 2 ounces (2 shots) of espresso.
Substituting with Coffee: Use 1/4 to 1/2 cup strong coffee, dark recommended.
Quick Latte: If you don't have time to make the sauce in advance. Combine espresso shot, milk, 1 to 2 tablespoons of maple syrup or honey, 1/4 to 1/2 teaspoon pumpkin pie spice, and 1 1/2 to 3 teaspoons pumpkin puree.