Line 8×8 baking pan with parchment paper and set aside. Also, preheat oven to 350℉.
Add dairy-free butter, granulated white sugar, brown sugar, and salt to the large microwave safe bowl and microwave for five one-minute intervals, stirring every interval until there butter is completely melted and the sugar is slightly dissolved.
While the butter and sugar melt in the microwave, mix together the boiling water and instant coffee in a small bowl until the coffee granules completely dissolve (or pull an espresso shot at this time if using an espresso machine). Set aside.
Once the butter and sugar are melted, remove from microwave and whisk until combined. Then, add instant coffee (or espresso shot), cocoa powder, vanilla extract, and oil to the butter and sugar and whisk until combined.
Add the gluten-free baking flour and corn starch to the large bowl and whisk until combined.
Once flour is mixed in, add the eggs one at a time. Vigorously mix in each egg at high speed for 1 minute. After adding eggs, continue mixing on high speed for 3 minutes until the batter has many air bubbles and is slightly lighter in color.
After whisking, quickly fold in chocolate chips and immediately pour batter in lined baking pan.
Bake at 350℉ for 35-40 minutes or until the brownies at the center of the pan are no longer jiggly.
Once ready, sprinkle sea salt over hot brownies and set aside to cool completely (about 45 minutes). For best results, store in the refrigerator overnight.