To make the tart dough: In a medium-sized bowl, beat butter and sugar on medium speed until mostly combined. Add eggs one at a time, and mix well after each. Next, add salt. Then add flour in three or four stages, mixing on low-speed after each addition until just combined. Scrapes the sides of the bowl as needed. Spray two muffin pans with nonstick-spray. Lightly flour a clean, flat surface, such as a table or kitchen counter. Scoop dough into balls and roll them out on the floured surface. Each circle of dough should be 4-5 inches across. (If the dough is too sticky, even after rolling it in flour, let it sit in the refrigerator until firm.) Gently lift the circles of dough and place one in each cavity of the muffin pans. Lightly press dough onto bottom and up sides of each cavity. Trim off the top of the dough as needed. Place muffin pans in the refrigerator while you mix the brownie batter.
To make brownie batter: In a microwave-safe bowl or glass measuring cup, cut butter into chunks and microwave in 30 second intervals until melted. While butter is melting, measure out 1/2 cup of chocolate chips. Transfer melted butter and chocolate chips to a medium-sized bowl and whisk until the chocolate melts completely. Next, whisk in sugar, cocoa powder, milk, cinnamon, and vanilla. Add eggs and whisk until incorporated. Carefully whisk in flour, making sure to mix until just combined. Stir in 3/4 cup chocolate chips. (You can add more or less depending on your preference.)
Remove muffin pans from refrigerator and preheat oven to 350 degrees. Spoon brownie batter into the prepared muffin pans, about 3/4 full. Bake for 25-30 minutes, or until dough is lightly browned and tops of brownies are cracked. Let Townies cool in the pan for about 5 minutes, and then transfer to a wire rack to cool faster. Townies are best if they are still a little warm.