It is important to get the sugar granules to completely dissolve for kaju katli. The sugar syrup should feel thick and sticky between the fingers and form a brittle string between your fingers as pictured here. If you have a candy thermometer, just wait for the sugar syrup to get between 215 F and 235 F (sugar string stage) before adding the cashew flour. But more importantly, don't allow the sugar to get too hot or else the kaju katli will crystalize into a hard ball.