Heat the oven to 350°F and line your baking sheets with parchment paper.

In a medium bowl, whisk together the flour, salt and baking powder, then set it aside.

Put the cold, cubed butter in the bowl of a stand mixer and beat it until it turns light and fluffy.

Add the brown sugar and white sugar and keep beating until everything is creamy and well blended.

Mix in the eggs and vanilla until fully combined.

With the mixer on low, add the flour mixture a third at a time, letting each addition blend in before adding the next.

Switch to a wooden spoon and stir in the M&M's, pretzels, Oreos, Reese's and sprinkles until they're spread evenly through the dough.

Scoop the dough onto the prepared sheets, leaving room between each cookie, and bake for 10 to 12 minutes, until the edges are golden and the centers still look slightly soft.

Let the cookies cool on the pan for a few minutes before moving them to a wire rack.