Put all the filling ingredients in a bowl and beat them together with a spoon until smooth and combined. It is important that the cream cheese is at room temperature or your filling may be lumpy.
Put the bowl of filling in the freezer to chill while you prepare the streusel and muffin batter. *If you are making this ahead of time, just put it in the fridge, we don't want it to freeze, just to get cold and firm up a bit.
Make the Cinnamon Streusel Topping
Put all the dry ingredients in a bowl and whisk together.
Melt the butter in the microwave and pour ¾ of it into the dry ingredients. Mix with a fork until combined. Add a little more butter at a time, mixing in between until the mixture looks like chunky, wet sand. You may not need all of the butter. Set aside.
Make the Pumpkin Muffins
Preheat the oven to 425°F / 220°C and line a muffin tray with muffin liners.
Sift the flour, both sugars, spices, baking powder, baking soda, and salt into a large bowl and mix to combine.
In a separate bowl, melt the butter in the microwave, then add to it all the other wet ingredients. Whisk together to combine.
Pour the wet ingredients into the dry ingredients and whisk together until smooth and free from lumps.
Scoop or spoon a small amount of muffin batter into the bottom of each muffin liner - about 1-2 tablespoons.
Remove the cream cheese filling from the freezer, it should be cold and fairly firm (i.e. not runny).
Use a teaspoon or a small melon baller to scoop dollops of cream cheese filling. Place them in the center of each muffin. Try not to keep the cream cheese in the middle of the muffin so it doesn't touch the sides.
Once all the muffins are filled, put more muffin batter on top, filling them all the way to the top of the case.
Sprinkle each muffin generously with streusel topping, and press down very gently to push the streusel into the batter.
Place the muffins in the center rack of the oven and bake for 7 minutes. Then turn the temperature down to 350°F / 180°C and continue to bake for another 15 - 20 minutes. Once the muffins are ready they should be slightly springy to touch and a skewer inserted should come out clean (be careful to avoid the filling!).
Notes
Make sure you use pumpkin puree and not pumpkin pie filling. To get bakery-style domes on your muffins, bake them at a high heat first, then turn the temperature down for the remainder of the bake time - see post above for more info.