125 ml(½ cup) lukewarm milk28 gmdry yeast (4 sachets)65 gmraw caster sugar, plus extra for glazing600 gm(4 cups) plain flour125 gmbutter, softened2egg yolks180 ml(¾ cup) pouring cream1egg yolk, mixed with 1 tbsp of water, for eggwashFor dusting:pure icing sugarTo serve:mascarponePeach jam6yellow peaches, scored100 gmraw caster sugarGrilled peaches5yellow peaches, halved, stones removed75 gm(1/3 cup) raw caster sugar
Combine milk, yeast and 1 tbsp caster sugar in a bowl. Set aside until foamy (5-10 minutes). Sift in 50gm flour and stand until foamy (5-10 minutes). In the bowl of a food processor with a dough attachment, sift in remaining flour and pinch of salt. Add butter and remaining sugar and beat until pale. Change attachment to a dough hook, add flour and yeast mixture, egg yolks and cream and process until a smooth dough forms (5-10 minutes). Turn onto a work surface and knead until smooth and elastic (3-5 minutes). Transfer dough to a bowl, cover with plastic wrap and stand in a warm place until doubled in size (1-2 hours).
Preheat oven to 200C. Meanwhile, for peach jam, blanch peaches until skins split (10-20 seconds), then refresh. Drain, then peel peaches (discard skin), coarsely chop flesh (discard stones) and place in a saucepan with sugar and cook over medium-high heat, stirring occasionally, until jam consistency is reached and volume has reduced to 375ml (20-30 minutes). Set aside to cool.
Knock back dough and roll out to a 65cm-long log shape. Twist log, bring ends together and knot to seal. Transfer to a baking paper-lined oven tray, bake for 15 minutes, then reduce heat to 170C. Brush cake with eggwash, scatter with extra caster sugar and bake until cooked through and golden (30-35 minutes).
For grilled peaches, preheat a grill to high. Place peach halves, cut-side up, on an oven tray and scatter with sugar. Grill until golden and bubbling (5-10 minutes). Serve cake warm, dusted with icing sugar, topped with grilled peaches, and with peach jam and mascarpone to the side.