Preheat the oven to 190°C (170°C fan). Fill your muffin tins with paper muffin cups. This recipe will make around 22 medium muffins. My muffin tin has 12 cups as seen on the pictures.
Mix the first five dry ingredients (all purpose flour, whole-wheat flour, pumpkin spice, baking soda and salt) together in a bowl.
In a bigger bowl, whisk together pumpkin, brown sugar and maple syrup. Add in eggs, vegetable oil and vanilla extract. Mix well.
Slowly add the dry ingredients to the pumpkin mixture and mix until just combined and no more dry flour is visible. Do not overmix.
Use around 1 tablespoon of batter to fill the muffin cups about ¾ full. Adjust if using bigger or smaller muffin tins.
In another bowl, mix cream cheese until soft. Stir in sugar, egg yolk and vanilla extract and beat until smooth.
Top each muffin with a teaspoon of cheesecake mixture. Use a toothpick to swirl the cheesecake mixture into the muffin batter.
Optional: Make the walnut crumble by combining brown sugar, chopped walnuts, flour, oil and pumpkin spice. The crumble should form little clumps but still be crumbly (as the name suggests). Top the cupcakes with a teaspoon of the walnut crumble.
Bake for 18-22 minutes or until the tops are slightly browned and a toothpick inserted to the middle of the cupcake comes out clean.
Let cool for a few minutes in the muffin tin and then transfer to a cooling rack to cool completely.
When completely cooled, the cupcakes can be stored in the fridge in an air-tight box for 3 to 5 days.