Whisk together the flour, baking powder and salt in a medium bowl. Beat the butter and sugar in a large bowl with an electric mixer on medium-high speed until light and fluffy, 3 to 5 minutes. Beat in the egg and vanilla until incorporated. Reduce the mixer speed to low; add the flour mixture and beat until just combined.
Shape the dough into a rectangle and cut into 6 equal pieces. Return one piece to the mixer and add 4 to 5 drops red food coloring. Mix on low until evenly colored a vibrant red. Shape into a log and wrap in plastic. Clean the mixer bowl and paddle. Add 3 pieces of the remaining dough to the mixer bowl and add 1 to 2 drops black food coloring. Mix on low until evenly colored light grey. Flatten into a rectangle and wrap in plastic. Leave the remaining 2 pieces of dough uncolored. Flatten them into a rectangle and wrap in plastic. Refrigerate all the dough until they just begin to firm up, about 20 minutes.
Cut a piece of pliable cardboard into a 10-inch square and cut a piece of parchment to fit on top. Fold in half to crease the cardboard and parchment. Roll the grey piece of dough on a lightly floured work surface to make a 7-by-8-inch rectangle, making the edges slightly thinner than the center. Center the rolled dough on the crease of the parchment with the 7-inch side closest to you and fold the cardboard to make a deep "V." Brush just the crease with egg wash. Place jars or cans on either side to hold the cardboard V in place while you roll the rest of the dough.
Roll the plain piece of dough to a 7-by-8-inch rectangle and place on top of the grey rectangle. Brush the entire piece with egg wash. Roll the red log into a 4-inch cylinder. Cut in half lengthwise to make two 4-inch half-moons. Place the red pieces in the crease, rounded-side down, and press gently to adhere. Fold the edges of the plain dough over to completely cover the red and press to adhere. Trim the edges of the grey dough so they are even with the plain dough. Using the cardboard as a guide, gently press the top and side to make the dough into a triangle shape (Don't press too hard, though). Wrap the dough in the parchment, then plastic. Freeze until solid, about 2 hours.
Preheat the oven to 350 degrees F. Position racks in the upper and lower thirds of the oven. Line 2 baking sheets with parchment.
Cut about 1/2 inch off each end of the cylinder with a very sharp knife to reveal the shark face. Slice the cylinder into about 1/4- to 1/3-inch-thick cookies. Arrange the slices about 1 1/2 inches apart on the prepared baking sheets. With a paring knife, cut 3 small diagonal slits in the grey part of the cookies for gills, starting about halfway down. Bake, rotating the pans halfway through, until crisp and just starting to turn brown on the bottom, 10 to 12 minutes.
While the cookies bake, melt about three-quarters of the white chocolate in a microwave-safe bowl in the microwave on 50-percent power. Stir until smooth. Transfer to a resealable plastic bag and snip a small corner from one end for piping.
As soon as the cookies come out of the oven (they should be still hot/warm), press mini chocolate chips points-up around the jawline to make teeth. The chips will adhere as the cookies cool. Pipe 2 small dots of melted white chocolate on each side of the cookies, near the top, and stick mini chocolate chips on for eyes.
Once the cookies are cool, pipe the remaining white chocolate in a wave along the bottom of each cookie and dip in the blue sprinkles to make the ocean. Let harden on parchment before serving.
When measuring flour, we spoon it into a dry measuring cup and level off excess. (Scooping directly from the bag compacts the flour, resulting in dry baked goods.)
Copyright 2018 Television Food Network, G.P. All rights reserved.