Preheat the oven to 350˚F. Line a 9x13 inch baking pan with parchment paper and set aside.
In a medium bowl, mix together the flour, cocoa powder, salt and baking soda. Set aside.
In the bowl of a stand mixer, cream together the butter and sugar until light and fluffy. Add in the eggs one at a time, mixing after each addition. Mix in the vanilla.
Slowly add in the red food colouring until it reaches your desired colour.
Slowly mix the dry ingredients into the wet ingredients until just combined.
Pour the batter into the prepared baking pan and bake in the preheated oven for around 15-18 minutes, or until a toothpick inserted comes out clean. Allow to cool completely.
In the bowl of a stand mixer, cream together the butter and cream cheese. Slowly add in the powdered sugar until fully incorporated. Mix in the vanilla.
Frost the cooled bars and decorate with sprinkles.