In a large mixing bowl, cream the butter and sugar on medium-high speed until light and fluffy, about 2 minutes. With a wooden spoon or spatula, mix in the flour, sweetened condensed milk and vanilla until incorporated and smooth. Next, Stir in the chocolate chips. Cover with plastic wrap and place in freezer for 5 minutes until the mixture is firm enough to form balls.
Shape the chilled cookie dough mixture into 1 inch balls, place on a parchment paper lined baking sheet and place back in the freezer for 5 minutes.
While the balls are in the freezer, start melting the chocolate. There are two methods; one easier and one safer. If using the microwave method, place chocolate in a bowl and microwave in 30 sec increments, stirring frequently until the chocolate is melted. If using the broiler method; bring 1 cup of water to simmer in a small sauce pan. Place the chocolate in a heat proof bowl and place eon the simmer pan, mix frequently until the chocolate is fully melted.
Using a fork or toothpick, dip each truffle, one at a time into the melted chocolate until fully coated. Place back on parchment paper. If the balls are too soft or are not holding up, place them back in the freezer for 5 minutes to become harder. After all the truffles are dipped, place back in the freezer for 5 minutes; remove from freezer and drizzle with remaining chocolate.
Store in the refrigerator and serve cold. Can also be frozen for longer storage. Enjoy!