O Tama Carey's rhubarb achcharu

Heat mustard seeds in a small saucepan over medium heat until they start to pop (40-50 seconds). Transfer to a mortar, add ginger and 1 tsp sea salt flakes and pound to a fine, dry paste. Stir in remaining spices. Bring vinegar, sugar, spice mix and 100ml water to the boil in a small saucepan, then reduce heat to low and simmer until slightly thickened (3-4 minutes).Keep liquid at a bare simmer.

Meanwhile, heat a grill pan over high heat. Toss rhubarb batons in a bowl with oil, then grill until char marks appear (3 minutes), turn and char other side. As rhubarb batons are ready, add them to the simmering liquid. When all have been added, remove saucepan from the heat. At this stage the rhubarb should still be quite firm. Cool in the liquid, then refrigerate overnight to chill and pickle (overnight). Rhubarb achcharu will keep refrigerated in an airtight container for a good week or more. Serve at room temperature.