Combine farmer cheese, cream cheese, sugar, and egg yolks in a food processor and process until smooth.

Transfer the cheese mixture to a bowl and stir in lemon zest, lemon extract, and lemon juice.

Wrap the cheese mixture in a double thickness of damp cheesecloth and place in a colander set over a bowl.

Fold the ends of the cheesecloth over the top, place a small plate on the cheesecloth, and put a 2-pound weight on the plate.

Refrigerate overnight (approximately 8-16 hours).

Unwrap the cheese mixture.

Roll the cheese mixture into 1 1/2-inch balls.

Place the cheese balls on a plate and freeze for about 30 minutes to firm up.

Melt the chocolate and vegetable shortening in a heavy saucepan over low heat, stirring constantly.

Allow the melted chocolate to cool to lukewarm.

Remove the cheese balls from the freezer.

Insert a toothpick into the center of one cheese ball.

Dip the cheese ball into the melted chocolate, coating it completely and allowing excess chocolate to drip back into the pan.

Place the chocolate-covered cheese ball on a wax paper-covered plate.

Remove the toothpick and dab a small amount of chocolate over the toothpick hole to seal it.

Repeat the dipping and coating process with the remaining cheese balls.

Refrigerate the chocolate-covered cheese balls until the chocolate sets.