Preheat the oven to 375 degrees Fahrenheit.
Add 1 cup unsweetened soy milk, 3/4 cup pumpkin purée, 1/2 cup pure maple syrup, 1/2 cup creamy almond butter, and 1 teaspoon vanilla extract to a mixing bowl, then use a whisk to mix well.
Add 2 cups whole wheat flour (spooned into the measuring cup, then leveled, not scooped), 4 teaspoons baking powder, 2 teaspoons pumpkin pie spice, and 1/4 teaspoon salt to a separate bowl, then mix well.
Transfer the dry ingredients into the bowl with the wet ingredients, then use a spoon to mix to combine. Mix in any optional additions at this point (see notes below).
Divide the batter evenly into 12 portions in a muffin pan lined with paper baking cups.
Bake for 22 minutes or until a toothpick inserted into the center of a muffin comes out looking clean.
Let the muffins cool for at least 30 minutes before removing from the pan and serving.