In a large mixing bowl or the bowl of the stand mixer, cream butter and sugar together until light and fluffy.
Add the milk and vanilla extract and mix until combined.
In a mixing bowl, combine flour, custard powder, milk powder, ground cardamom, baking powder, salt and the mixed fruits and nuts. Whisk well.
Add the flour mixture to butter mixture and mix until a smooth dough forms.
At this point, the dough can be rolled out, cookies can be cut using a cookie cutter and baked right away. Or can be formed into a log, wrapped in plastic wrap and refrigerated for at least 1 hour or up to 3 days. When ready to bake, slice the log into ½” slices and bake.
To Bake: Preheat the oven to 350°F and line a baking sheet with parchment paper. Place the cookies 1″ apart and bake for 13~15 minutes or until the cookies are slightly firm and lightly golden around the edges.
Remove the baking sheet from the oven and let the cookies cool completely on the baking tray. Store in an airtight container for up to a week.