Instructions

1. Soften the butter to room temperature or microwave for 15-20 seconds until softened but not melted.
2. Combine the butter with the sugar and beat on medium speed until well creamed together.
3. Add the milk, egg, and vanilla extract. Mix until it’s well combined.
4. In a separate bowl, combine the remaining dry ingredients. Slowly add into batter and beat on medium low speed until well combined and dough forms.
5. Melt the chocolate in the microwave in 30 second increments, stirring occasionally until melted and smooth.
6. Divide the dough in half (about 8.5 oz each) and mix the chocolate into one half of the dough.
7. Turn each dough out onto a lightly floured surface and roll out until is 1/8 inch thick into a rectangle shape. The shapes should be similar in size.
8. Place the chocolate dough over the regular dough and gently press together with the rolling pin. Trim excess edges.
9. Roll the dough into a log, tightly wrap in plastic wrap. Chill the dough for at least 2 hours in the refrigerator or 1 hour in the freezer.
10. Slice the dough into ¼ inch thick slices. Bake cold,  placing on a baking sheet lined with parchment paper or a silicone baking mat. Bake at 425°F for 5-7 minutes.