Another reason for this custom is that the Ancient Israelites did not know the laws of kashrut before they received the Torah at Mount Sinai. They ate dairy foods until they could learn and follow the laws of kashrut.
A favorite treat to serve during Shavuot is ice cream. You can make your own with a few simple ingredients.
2 cups milk or heavy cream
½ cup sugar
2 tsp. pure vanilla extract
Resealable plastic bag
Large plastic bag
¾ cup salt
3 cups ice
Place the milk (or cream), sugar, and vanilla extract in the sealable bag. Seal it tightly.
Place it in the second bag.
Add the ice and salt.
Tie the bag tightly.
Shake well for about 10 minutes.
Alternatively, you can put the bag with the ice cream mix in the freezer. Take it out and shake it every 10 minutes until it reaches the desired consistency.