Preheat oven to 350 degrees Fahrenheit.
Line a muffin tin with cupcake liners or muffin liners, or spray with cooking spray.
In a medium mixing bowl, mix together the dry ingredients (sugar, flour, baking soda, salt, cinnamon, nutmeg, and all spice).
In a large mixing bowl, combine the bowl of wet ingredients (pumpkin purée, eggs, sourdough discard, avocado oil, heavy cream, and vanilla). Mix well until blended completely.
Add the dry ingredients to the wet ingredients (mix slowly with a stand mixer or hand mixer, be careful not to over mix). Mix until fully combined and no lumps remain.
Fill each muffin cup with batter (approximately 1/3 cup).
Place the muffins into the preheated oven on the center rack. Bake for 26-30 minutes, be careful not to over cook. Complete the toothpick test - insert a toothpick into the center of the muffin and it if comes out clean the muffins are ready.
Let the muffins cool for 5-10 minutes and enjoy!