Line 5-3/4-x 3-1/4-inch (625 mL) loaf pan with plastic wrap; set aside.
In saucepan, melt together chocolate, butter and sugar over medium-low heat until smooth. Whisk in egg yolks, one at a time; cook, stirring, for about 3 minutes or until thickened and glossy. Transfer to large bowl; let cool to room temperature.
In separate bowl, whip cream; fold one-quarter into chocolate. Fold in remaining whipped cream. Spoon into prepared loaf pan. Cover and refrigerate for at least 8 hours or until firm. (Make-ahead: Refrigerate for up to 2 days.) To unmould, gently pull on plastic wrap to loosen top edge of pate from pan; unmould onto cutting board. Cut into 8 slices.