1Melt the butter and 3 oz of the chocolate in a small saucepan over low heat, stirring constantly with a metal spoon until smooth. Remove from the heat and set aside to cool slightly.
2Put the flour, salt, brown sugar and cocoa powder in the bowl of a stand mixer with the paddle attachment. Mix on low speed until combined. Add the warm chocolate mixture and the egg. Mix on low speed until combined.
3Chop the remaining 4 oz chocolate and stir into the dough.
4Insert the wire rack into the middle shelf position. Preheat the oven. Select BAKE/350°F/CONVECTION/13 minutes and press start.
5Line the pizza pan with parchment paper. Roll heaped tablespoons of dough into balls. Place 6-7 balls evenly spaced on the pan, not too close to the edge, allowing room for spreading. Flatten slightly.
6Once preheated, put the cookies in the oven and bake for 13 minutes until the cookies are cracked a little on the surface. Remove from the oven and cool on the pan for 5 minutes. Then transfer to a wire rack to cool completely.
7Repeat with the remaining dough.
8Dust with a little cocoa powder to serve.
9Store the cooled cookies in an airtight container for 4-5 days.