Preheat the oven to 350 degrees F. Line a baking sheet with parchment paper.
Whisk the flour, granulated sugar, cornmeal, rosemary, baking powder and salt together in a large bowl. Whisk together the melted coconut oil and eggs in a small bowl and add to the dry ingredients, stirring just until combined. It will look crumbly at first, then sticky. Stir in the white chocolate chips.
Heavily dust your work surface with powdered sugar and turn out the dough. Knead until smooth, then shape into a 10-by-2-1/2-inch slightly flattened log and transfer to the prepared baking sheet. Bake until golden and firm, 25 to 30 minutes. Set aside until cool enough to handle, 10 to 15 minutes. Reduce the oven temperature to 300 degrees F.
When cool enough to handle, place the dough log on a work surface and cut crosswise with a serrated knife into 1/3- to 1/2-inch-thick pieces to form individual cookies. Put the cookies back on the same baking sheet lying flat. Bake until golden brown and firm, about 30 minutes, flipping halfway through. Let cool before serving. Store in an airtight container for up to 10 days.