Pre heat the oven to 350 Degrees F (180 Degrees C).
Line a baking sheet with parchment paper.
Transfer butter, dark brown sugar and castor sugar in the bowl of the blender.
Whisk for 3-4 minutes on medium speed.
Add milk and vanilla extract and mix well.
Add all purpose flour and baking soda in the bowl and mix until combined.
Fold chocolate chips and m&m in the dough.
Scoop 1 tbsp of the dough on the parchment sheet keeping a distance of 2 inches between each scoop.
Bake the cookies for 12-13 minutes until the sides are slightly browned.
Transfer the cookies on a wire rack and cool completely.
Make all the cookies in the same manner.
Store in a glass jar
After adding the flour, do not mix the batter too much.You can increase the amount of M& M and chocolate chips if you like the cookies more loaded.Make sure to scoop the batter keeping a distance with each other.