A few weeks ago when I made the Key Lime Pie, I had a couple of limes leftover. I also had some macadamia nuts and white chocolate chips in my freezer which needed to be used. So I decided to make the traditional WC Mac Cookies but thought the limes would be a nice addition.
I zested two of the Key Limes and tasted the batter. I could barely taste the lime so I had a regular Persian lime which I zested and added to the batter for a more prominent lime flavor, but not strong.
After baking, however, the lime flavor was again a bit faint (although the taste results in a great white chocolate macadamia cookies).
So if you want to add lime to to the recipe, you'll need to experiment to your taste. Personally, I would start with the zest of 2-3 Persian limes. Taste the batter as you go along. I'd probably add some lime juice to it also. I will suggest tweaking the recipe until the batter is just a twinge past tart. The tartness will dissipate a bit while baking.
WHITE CHOCOLATE MACADAMIA NUT COOKIES with (optional) LIME
1 cup butter, softened
1 cup sugar
3/4 cup brown sugar
2 tsp vanilla extract
2 large eggs
3 cups AP flour
1 tsp baking soda
1 cup white chocolate chips
1 cup macadamia nuts
Lime zest and juice to taste, optional
Preheat oven to 375F.
Cream together butter and sugars until fluffy. Add the vanilla and eggs until well combined.
Stir in the flour, baking soda, and salt and mix until just combined (be careful not to over-stir the batter). Add the white chocolate chips, macadamia nuts, and the zest and/or juice of limes, if using.
Chill dough in refrigerator for at least a couple of hours (I generally make my dough one day and bake the next).
Drop by rounded Tablespoons onto a cookie sheet lined with parchment paper or a Silpat, placing them about 2" apart.
Bake for 10-12 minutes (for softer cookies remove from the oven when the edges start to turn golden. Leave a little longer for crispier cookies.)