Preheat oven to 275 degrees. Line a baking sheet with parchment paper and set aside.
In a small pan, set over low heat, melt 1 1/2 cups chocolate chips, stirring constantly. Once the chocolate is melted, mix in the instant coffee, then set aside.
In the bowl of a stand mixer, add the egg whites. Using the whisk attachment, turn the mixer on to medium-high speed and beat until the egg whites until stiff peaks form and the meringue does not slide around when the bowl is turned on it’s side.
Gradually mix in the sugars, vanilla, lemon juice, salt and corn starch and continue beating for several minutes. You want the egg whites to be glossy and, when you pinch it between your fingers you should barely feel any sugar granules.
At this point, pour the melted and cooled chocolate and coffee mixture on top. Do not stir it in. Simply scoop spoonfuls of the mixture out and drop them on the lined baking sheet.
The chocolate will swirl in automatically as you do this. Depending on what size you make your cookies, you should be able to fit 9-12 on a sheet.
Bake them for 40-50 minutes, or until they’re slightly golden brown and they can easily slide off the baking sheet. Remove cookies to a baking rack and allow to cool. Repeat this process until you’ve used up all of the batter.
If you’d like to add a chocolate bottom to your cookies, simply melt the remaining 1/2 cup of chocolate chips in a small pan over low heat, constantly stirring.
Once it’s melted simply dip the bottoms of the cookies in and then lay them upside down on the cooling rack until the chocolate has hardened. You can also use a knife to spread the chocolate on the bottom of each cookie.
Once the cookies have cooled and the chocolate has hardened, store them in an airtight container.