Préhéât thé ovén to 350°. Buttér thé insidé of 9”-×-13” inch bâking pân ând liné with pârchmént pâpér.
In â médium bowl, whisk togéthér thé flour, sâlt, ând cocoâ powdér.
Sét â lârgé héâtproof bowl ovér â sâucépân of simméring wâtér to créâté â doublé-boilér. âdd thé buttér ând thé chocolâté chips to thé bowl. Héât, stirring occâsionâlly until thé chocolâté ând buttér âré complétély méltéd ând smooth. Turn off thé héât, thén whisk in thé sugârs ând stir until combinéd. Rémové bowl from héât.