Preheat the oven to 350 F. Line a 12 cup muffin pan with paper liners. In a medium bowl, whisk flour, salt, and baking soda together. In a large bowl, mix butter with peanut butter, granulated sugar and brown sugar until fluffy.
Add in egg and vanilla extract and mix until smooth. Add in the flour mixture until it is fully combined. Fold in the M&Ms, white chocolate chips and sprinkles. Evenly divide the cookie dough between the paper liners. Bake for 12-15 minutes.