Step 1Melt the butter in a heavy pot over low heat. Whisk in the sugar, water and salt, scraping down the sides. Bring the mixture to a boil, and do not stir until the toffee begins to color. When it is the color of peanut butter, add the coconut, stirring to combine. Spread onto a rimmed baking sheet so the toffee is no thicker than 1/4 inch. Cool, then break into pieces about 2 inches in diameter. This makes more toffee than is needed for the rest of the recipe; the toffee will keep, in an airtight container at room temperature, up to five days.
Step 1In a large bowl, whisk together the oats, flour, baking powder and soda, salt and wheat germ. Set aside.
Step 2In the bowl of a stand mixer using the paddle attachment, cream together the butter with the two sugars until light and fluffy, 6 to 8 minutes. Scrape down, add the egg and vanilla and beat to combine. Scrape again, and add the dry ingredients in two additions, beating just until combined. Wrap the dough tightly in plastic wrap and refrigerate overnight.
Step 3Heat the oven to 375 degrees. Portion the cookies using a 1/4-cup measuring cup. Roll each cookie into a ball, then flatten slightly, sprinkling a little kosher salt on the edges. Space the cookies a few inches apart on a baking sheet (they will spread), and bake for 10 minutes. Remove from the oven and place a piece of toffee on top of each cookie, pressing down on each gently.
Step 4Return to the oven and bake until the cookies are a dark golden color and the edges of the toffee have melted, 5 to 7 minutes more.