Preheat oven to 350F. Line two baking sheets with parchment paper. Lightly crush 2 cups of cornflakes with your hands into rough, flaky pieces, leaving some whole for texture. Reserve the remaining 0.5 cup for topping.

In a large bowl, beat softened butter and sugar with an electric mixer on medium speed until light and fluffy, about 3 minutes. Scrape down the bowl. Beat in eggs one at a time, then mix in vanilla until just combined.

Add flour, baking soda, and salt. Mix on low speed until a soft dough forms with no dry streaks remaining. Do not overmix.

Switch to a wooden spoon or rubber spatula. Fold in the 2 cups crushed cornflakes and shredded coconut until evenly distributed. The dough will be thick and slightly chunky.

Using a 1.5 tablespoon cookie scoop or heaping tablespoon, drop dough onto prepared sheets 2 inches apart. Press a few reserved cornflake pieces into the top of each cookie for extra crunch.

Bake 10-12 minutes, rotating pans halfway through, until edges are golden brown and centers look set but still slightly soft. The cookies will look puffy and underdone in the middle - they firm up as they cool.

Cool on the baking sheet 5 minutes, then transfer to a wire rack to cool completely. Store in an airtight container at room temperature up to 5 days.