Preheat oven to 300 degrees (F). Line two large baking sheets with parchment paper, lightly spray them with non-stick spray, and set aside.
Place the semi-sweet chocolate chips and butter in a small, microwave safe bowl. Heat them in the microwave for for 15 second increments of time, mixing in between each, until butter and chocolate are completely melted and can easily be whisked smooth. Set aside. *You may also do this process on the stove top if you don't own a microwave.
In a medium-sized bowl whisk together the flour, cocoa powder, baking powder, and salt: set aside. In a separate medium-sized bowl whisk together the sugars, eggs, milk, and vanilla.
Add the dry ingredients into the wet ingredients, and stir to combine - be sure not to over mix here!
Fold in the chocolate/ butter mixture and the toffee bits into the batter, stirring until everything is just combined.
Using a lightly greased measuring cup, scoop 1/4 cupfuls of the batter on the prepared baking sheets. Baking one pan at a time, place the cookie sheet in the oven and bake for 18-20 minutes, or until the tops of the cookies are set and glossy. Press a chocolate kiss into the top of each warm cookie and set aside to cool completely. Once cool, drizzle with the chocolate glaze and decorate with chopped toffee if desired. Let the chocolate drizzle set before serving (about 10 minutes at room temperature; 5 minutes in the fridge). Repeat with second batch of cookies.
For the chocolate glaze:
Combine the chocolate and oil in a small microwave safe bowl. Heat them in the microwave for 15 second increments of time, mixing in between each, until oil and chocolate are completely melted and can easily be whisked smooth. Drizzle on cooled cookies, then decorate with toffee, if desired.