To make the whipped cream, add the heavy cream to a mixer fitted with the whisk attachment. Whisk on high until soft peaks form and the cream holds to the whisk when lifted out of the bowl. Fold in the powdered sugar and lemon zest. Place in the refrigerator while making the shakes.
To make the milkshakes, combine the lemon curd, ice cream, and milk in a blender. Purée until smooth, about 15 to 20 seconds. Pour an even amount of the shake into each of four glasses. Crumble half of a cookie over each shake. Top each with an equal amount of the whipped cream. Crumble the remaining half of a cookie over each dollop of whipped cream. Top with a lemon slice and serve.
**You can make your own lemon curd using the recipe below. This recipe makes about 1 cup of curd.
Fresh Lemon Curd
½ cup freshly squeezed lemon juice*
⅓ cup sugar
2 egg yolks
1 whole egg
Pinch of salt
6 tablespoons of unsalted butter, cubed
Zest of 1 lemon*
¼ teaspoon pure vanilla extract
To make the lime curd, use a double boiler. Add the lime juice, sugar, egg yolks, and egg to the pan. Heat the water as you stir together the ingredients until smooth. Bring the water close to a boil and then reduce it to a simmer, adjusting as needed during cooking.
Add the butter and salt to the lime curd. Continue to stir constantly until the butter is melted and the mixture begins to thicken. It is done when it begins to hold its shape when stirred, after about 10 to 15 minutes. Remove it from heat, and stir in the lime zest and vanilla. (If solids formed during cooking, pour the curd through a strainer set over another bowl, and gently stir the curd to press it through the strainer.) Allow the curd to cool.
*We recommend using lemons and limes from Paramount Citrus. They are consistently fresh and juicy and available at most major grocery, mass and club retailers.
Recipe courtesy of Wonderful Citrus.