Giant peanut butter chocolate chunk birthday cookie with sweetened condensed milk buttercream

Lightly grease a 12 to 14 inch pizza pan; a smaller pan makes a thicker cookie.

Whisk the all-purpose flour, baking soda, baking powder and fine sea salt together.

Mix two sticks of unsalted butter with the peanut butter for a minute.

Add light brown sugar and granulated sugar and beat until light in color, fluffy and aerated.

Add two eggs one at a time, scraping well after each, then the vanilla extract.

Mix in the dry ingredients until incorporated.

Mix in 4 oz milk chocolate and 4 oz dark chocolate, chopped into chunks of varied size.

Dollop the dough onto the pan and press into an even layer near the edge, leaving room to spread (all the way to the edge in a skillet or cake pan).

Bake at 375 F until evenly golden, darker at the edge, erring on the side of underbaking.

Cool completely.

With the whip attachment, whip two sticks of room temperature unsalted butter with the salt a good long while, scraping midway, until white and increased in volume.

Add one can of sweetened condensed milk slowly and gradually; if it separates, keep whipping, faster if needed.

Add vanilla. Dye portions of the frosting three colors.

Spread the colors side by side on plastic wrap, roll into a log, seal the ends, cut one end open and drop into a pastry bag.

Pipe the swirled frosting onto the cooled cookie and decorate with sprinkles; slice to serve.