In a food processor or blender grind up the pistachios until they are a sand- like texture.
In a large bowl mix together the pistachios, flour, baking powder and salt. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, cream together the butter and sugar until light and fluffy, a few minutes.
Add in the mascarpone and mix until incorporated. Add the eggs, milk, vanilla extract and almond extract, and mix once more. Note that the mixture will most likely be clumpy, but this is ok, the clumps of butter will melt nicely into the muffins.
Add the wet mixture to the dry ingredients and fold in with a spatula.
Optional step: cover the muffin mixture with cling wrap and set aside for one hour. This will give the leavener time to activate and give the muffins their dome shape.
Preheat the oven to 400f.
Line a muffin pan with 9 muffin liners. Using an ice cream scoop, place a small amount of muffin mixture into the liner. Then place the frozen pistachio cream disc on top, if using.
Finish by placing the rest of the muffin mixture on top of the pistachio cream.
Repeat for all 9 muffins.
Add the pistachio crumble to the top of each muffin.
Place the muffins in the oven. Bake at 400f for 10 minutes.
Drop the temperature down to 350f and without removing the muffins from the oven, continue baking for another 10-12 minutes or until a toothpick inserted comes out clean.
Let the muffins cool, remove from the tin and enjoy!