Preheat oven to 350°. Grease an 8” square baking dish with olive oil.
In medium bowl, sift together flour, salt, and baking powder.
In a large bowl, whisk together cocoa powder and boiling water, stirring until smooth. Whisk in melted chocolate, egg, and vanilla. Whisk in brown and granulated sugar. Fold flour mixture into the chocolate mixture, then add chocolate chips. Scrape into pan and cook for 20-25 minutes. Remove from heat and sprinkle with flaky sea salt. Cool before cutting.