Preheat the oven to 180°C, line the cupcake tin with muffincases and set aside. This recipe makes 9 muffins.
To make the crumble topping, stir together the flour andsugar. Add the melted butter and whisk with a fork until coarse crumbs form.Set aside.
To make the muffins stir together the flour, baking powder, and salt ina large bowl.
In a medium bowl, whisk together the egg and caster sugar until combined. Whisk in the yogurt, oil, and vanilla extract.
Add the dry ingredients into the wet ingredients and mix everything together, making sure not to over mix.
Finally fold in half of the rhubarb and raspberries, reserving the remainder for topping.
To assemble the muffins, add about 1½ tablespoons of muffin mixture to each muffin case. Using a spoon spread the mixture up the side of the muffin cases to make a small dent in the centre. Drop 1 heaped teaspoon of cream cheese into the centre of each muffin.
Add a few raspberries and rhubarb on top, then generously top each muffin with the crumble topping. Add a few more raspberries and rhubarb on top again, and gently press the crumbs to stick to the muffin batter.
Place in the preheated oven. Bake for 22-25 minutes, or until the tops are golden brown.
Cool for 5-10 minutes in the tray, then transfer the muffins on a rack to cool completely.