Good old rhubarb & custard with the best crumbly shortbread

INGREDIENTS

• 800 g rhubarb, washed and cut into 8cm pieces
• 4 tablespoons caster sugar
• zest and juice of 2 oranges
• 1 thumb-sized piece fresh ginger, peeled and finely grated
• 1 tablespoon balsamic vinegar
• 500 ml organic semi-skimmed milk
• 568 ml single cream
• 5 tablespoons caster sugar
• 1 vanilla pod, scored lengthways and seeds scraped out
• 8 free-range egg yolks
• 250 g unsalted butter, at room temperature, plus extra for greasing
• 125 g caster sugar, plus extra for sprinkling
• 250 g plain flour, sifted, plus extra for dusting
• 125 g semolina or cornflour