Preheat oven to 200 degrees Fahrenheit. Grease baking sheets with butter or PAM and sprinkle flour evenly. Or you can use parchment paper.
Using an electric mixer or hand mixer, start beating the eggs slowly until foamy. Once foamy add in the cream of tartar and increase speed. Once the egg whites have reached soft peak and without stopping the mixer. Add in the lime juice, aguardiente, and vanilla essence. After, add in the sugar a spoonful at a time.
At this point the speed on the mixer should be on high. Mix until you reach a hard peak. Lower speed on stir and put in the ground coffee until well incorporated. Spoon the mixture in a pastry bag or a heavy duty zip lock bag. Cut the corner of the bag and insert a pastry tip of any choice or you can do without it so you can pipe out the mixture onto the baking sheets. Pipe cookie-sized dollops about 1 inch apart.
Place the baking sheets in the preheated oven for 1 hour. 30 minutes into the baking rotate the baking sheets to ensure even cooking. After 1 hour of baking turn oven off and leave the meringues in the oven, letting it dry out. Let it cool completely in the oven before serving. (to make sure if your cookies are done, poke one and see if it’s dry and crisp, not mushy)
When serving garnish with the ground/chopped walnuts and mint leaves.