Preheat the oven to 350 F. In a medium bowl, whisk together flour, salt, and baking soda. In a large bowl, combine butter with peanut butter, and both granulated and brown sugar until fluffy.
Add in the egg and vanilla extract, and mix until it is smooth. Add in the flour mixture, and mix until it is fully combined. Fold in the sprinkles.
Roll the cookie dough into balls, and place them onto a large ungreased baking sheet. Bake for 10-12 minutes.