Place walnuts or pecans in the ziplock bag. Have your child/children beat the bag with a wooden rolling pin to break the nuts into pieces.
Let the children smell and taste the vinegar, then pour the vinegar into a mixing bowl.
Add the egg whites to the mixing bowl.
Add a pinch of salt to the bowl.
Finally, add the sugar and cardamom to the bowl.
Beat the bowl ingredients on high speed for approximately 15 minutes, or until stiff peaks form.
Fold the nuts into the egg whites.
Drop tablespoon-sized mounds onto two cookie sheets lined with parchment paper or silicone mats. Put the cookie sheets into the oven, close the door, and turn the oven OFF.
On Easter morning, have the kids unseal the oven and take a cookie. Point out the cracked surface and take a bite. Surprise, the cookies are hollow! Jesus is risen!!!