• Preheat your oven to 325° F / Prepare your baking sheets and line them with parchment paper or a silpat mat.
• In the bowl of a stand mixer, or using a hand mixer, combine the butter and sugar together on medium speed until it forms a creamy paste that is pale in color, 2-3 minutes.
• With the mixer on low speed, add in the egg yolks and whole egg, one at a time, mixing each addition thoroughly before adding the next. Continue to mix until everything is well incorporated.
• In a medium sized bowl, sift together the flour, corn starch, baking powder and salt.
• Add the flour mixture to your wet batter, little by little on low speed, allowing each addition to be fully mixed in. Add the lemon juice (or cognac, if using) and mix once more to combine.
• Transfer the dough onto a lightly floured surface and gently knead it a few times, just until it comes together. Wrap it in parchment paper or cling wrap and let rest in the fridge for at least 15 minutes.
• Roll out the dough with a rolling pin until it is about 1/4" thick; I like to work in sections, diving it into 3 pieces and working with one section at a time.
• Use your desired size of circle cutter to cut out the cookies and gently transfer them onto your lined baking sheets, leaving about 1/2"-1" space in between the cookies, as they will grow slightly while baking.
• Bake for 16 min, or until the edges are slightly turning golden brown; you want the cookies to still be fairly light in color, otherwise they will be too dry. Allow them to cool completely before assembling.

Assembling the Alfajores

• Spread a generous amount of dulce de leche in the center of a cookie and sandwhich another one on top, pressing lightly to allow the dulce de leche to reach the edges. Gently roll them in the desiccated coconut to finish.