Preheat the oven to 350F (180C). Place butter into a 9 inch (23cm) cast iron pan and melt over low heat. Add sugar, salt, cocoa powder and instant coffee. Mix to combine and remove from heat. Let cool slightly. Add vanilla extract and incorporate eggs one at time. Add flour and mix until well combined. Stir in chocolate chips. Spread 1 oz (30g) chocolate chips on top. Bake for 20-25 minutes until a toothpick inserted into the center comes out clean or with few crumbs. Serve warm with your favorite ice cream and chocolate drizzle.