Preheat the oven to 325ºF. Line an 8" round baking pan with parchment paper (or grease well with cooking spray). (You can use a 9" cake pan, but the cookie pie will be thinner and take a few minutes less to bake.)

In a large bowl, mix together the melted butter, oil and sugar to form a grainy paste.

Place the ⅓ cup chocolate chips in a small, microwavable bowl. Microwave the chocolate for 20 seconds, then stir. Microwave again, in 20 second intervals, stirring between each interval. Lower the time to 10 second intervals as the chocolate begins to melt. Continue microwaving until the chocolate has completely melted.

Add the melted chocolate to the sugar mixture. Mix until smooth.

Add the espresso powder, egg and vanilla. Mix well.

Next, add the flour and baking soda. Mix just until combined, being careful not to overmix.

Fold ½ cup of the chocolate chips.

Press the dough into the prepared pan. Then sprinkle the remaining ¼ cup chocolate chips on top of the dough and lightly press them in.

Bake for 25-26 minutes, until the cookie is cooked through.

Cool in the pan for 15 minutes, then remove the cookie to a wire rack to cool completely. Pull up on the sides of the parchment paper to remove the cookies from the pan.

Melt the ½ cup semi-sweet or dark chocolate in the microwave in the same way that you did for the cookies. Remember to melt it slowly, mixing in between intervals so it doesn't burn.

Drizzle the chocolate over the cookie pie.

Allow the chocolate to set, then cut the cookie into slices.

Store in an airtight container at room temperature.