Preheat oven to 325°F (160°C). Line 2 baking sheets with parchment paper.
In a glass bowl in microwave, melt shortening and semi-sweet chocolate chips on Medium (50%). Add in sugar and then eggs one at a time, stirring well after each addition. Let cool for 5 minutes.
Mix in sweetened condensed milk and vanilla. Add next 4 ingredients; mix well to combine. Cover with plastic wrap and refrigerate for 1 ½ hours up to 8 hours.
Sift icing sugar in a shallow bowl. Between palms of hand, roll pieces of chilled dough to form 1 ¼” (3 cm) balls. Drop balls into icing sugar and toss lightly until well coated. Place on prepared baking sheets and flatten very slightly. Repeat with remaining dough and remaining icing sugar, spacing about 1 ½” (4 cm) apart on baking sheet.
Bake each sheet in preheated oven for 11 - 13 minutes or until just beginning to feel firm when pressed in centre. Let cool on baking sheet on wire racks for 5 minutes. Transfer crackles to wire racks to cool completely.
Note: For a chewier, softer crackle, try Eagle Brand Regular Sweetened Condensed Milk.