In a large bowl with an electric hand mixer or in a stand mixer fitted with the paddle attachment, cream together the butter, granulated sugar, brown sugar, and corn syrup until light and fluffy, about 5 minutes.
Scrape down the sides of the bowl with a rubber spatula, then add the eggs and vanilla. Beat for 3 minutes, or until fully incorporated.
Add the flour, baking powder, baking soda, and salt and mix just until the dough comes together. Do not overmix.
Scrape down the sides of the bowl again, then fold in the white chocolate chips, sprinkles, oats, rice cereal, and fruit-shaped cereal.
Using an ice cream scoop or ¼ measuring cup (60 grams), scoop the dough onto a parchment-lined baking sheet. Cover with plastic wrap and refrigerate for at least 1 hour, or up to a 1 week.
Preheat the oven to 350°F (180°C). Line baking sheets with parchment paper.
Arrange the chilled dough balls 4 inches (10 cm) apart on the prepared baking sheets.
Bake for 6 minutes, then remove the cookies from the oven and place a corn chip in the center of each cookie to resemble a unicorn horn. Return to the oven for 6-8 minutes more, until lightly browned around the edges.
Let the cookies cool completely on the baking sheets before serving. The cookies will keep in an airtight container at room temperature for 5 days, or in the freezer for up to 1 month.