I started fiddling with this recipe pre-social distancing, and have gotten close to posting it twice, but then hesitated at the last second both times. The first attempt was just golden toasted coconut on shortbread. Tasty, but also a little dry. The second involved a can of sweetened condensed milk drizzled over the top before baking. The consistency was right, but the results were a little one note—they needed acid.This, the third and final go-round, has the zest and juice of two limes,* an egg yolk and a little salt stirred into that sweetened condensed milk, so that it bakes up reminiscent of Key Lime Pie filling. Yum!

*Yes, you can use lemons. Then they’ll be Coconut Lemon Squares.For those of you concerned about using only an egg yolk in a recipe right now (no food waste allowed in a pandemic!), you’ll be relieved to know that the white gets used in the coconut layer. It’s whisked together with sugar, salt and vanilla, and then used to coat a bunch of flaked coconut before baking.I used large-flake unsweetened coconut because that’s what I had on hand, but feel free to swap in a finer flake/shred style. If you’re using sweetened coconut, cut the added sugar in the topping to 1-2 tablespoons. I wouldn’t leave it out completely, as you want it to get really good and toasty and for the coconut below to be vaguely…marshmallowy? Sounds weird, yes, but that’s the word to describe its flavor, if not its texture. Trust me, it’s like a big macaroon and you’re going to love it.As for the crust, it’s just shortbread: flour, sugar, salt, cold butter. It’s crunchy, flaky and buttery—the perfect vehicle for the lime filling and coconut topping. I understand that a lot of people cannot get their hands on flour right now, so please note that you can use a graham cracker, Oreo (or Golden Oreo), or another crumb crust and it will work just fine. It may even be better…maybe I should have done a round four? Should I have bailed on posting at the last second again?

Oh lord. Somebody social distance me from myself.

Coconut Lime Squares
makes 1 8- or 9-inch pan, about 16 servings

Shortbread Crust:
1 1/2 cups all-purpose flour
1/3 cup granulated sugar
1/2 teaspoon Kosher or sea salt
3/4 cup (1 1/2 sticks) unsalted butter, cold

Lime Filling:
1 14 ounce can sweetened condensed milk
zest of 2 medium limes
3 tablespoons fresh lime juice (from about 2 medium limes)
1 large egg yolk
pinch of Kosher or sea salt

Toasted Coconut Topping:
1 large egg white, room temperature
3 tablespoons granulated sugar
1/2 teaspoon pure vanilla extract
2 cups flaked unsweetened coconut

Preheat oven to 350F. Line an 8- or 9-inch square pan with foil. Grease. Set aside.

Make the shortbread crust. In a medium mixing bowl, combine flour, sugar, and salt. Add cold butter. Use your fingertips to rub butter into flour until the largest pieces are the size of small peas. It will be powdery, but should hold together when pinched.

Pour shortbread mixture into prepared pan. Spread it around to cover the bottom of the pan before using the flat bottom of a measuring cup (or the heel of your hand) to pack it down into an even layer. Prick several times with a fork. Bake 10 minutes to set. Wipe out bowl (no need to wash) and set aside for coconut topping.

Make the lime filling. In a small mixing bowl, whisk together sweetened condensed milk, lime zest & juice, egg yolk, and salt. It may thicken slightly. Set aside.

Make the toasted coconut topping. In a medium mixing bowl (I use the same one I used for the crust), use a fork to whisk together egg white, sugar and vanilla, just until bubbly/a little foamy, about 1 minute. Use a silicone spatula or wooden spoon to fold in coconut.

Spoon lime filling over shortbread crust. Use a silicone spatula or the back of a spoon to carefully spread into an even layer. Scatter coconut filling over the lime filling, making sure to get it all the way to the edges. Press down lightly.

Bake 30-35 minutes, or until coconut is deeply toasted on top and center barely jiggles when pan is jostled. If coconut begins to burn during baking, tent with foil.

Let pan cool completely in a pan on a rack. Use foil overhang to transfer to a cutting board. Peel off foil. Use a large, sharp chef’s knife to slice into squares, wiping clean between cuts as necessary. Serve at room temperature or cold.

Squares will keep covered at room temperature for 3 days or in the refrigerator for up to 4.