Tip the flour, salt, cayenne, mustard powder, cumin or caraway seeds and some black pepper into the bowl of a food processor. Add the diced butter and use the pulse button to rub it into the dry ingredients. Add the grated cheeses and pulse again until the dough just comes together - you may need to add a drop of cold water.
Tip the dough out on to a lightly floured work surface and roll into a log roughly 5cm in diameter, wrap in clingfilm and chill in the fridge for a couple of hours or until firm.
Preheat the oven to 180°C/350°F/gas mark 4 and line a baking sheet with nonstick baking paper. Take the log out of the fridge, remove the clingfilm and brush with milk before coating in the sesame and kalonji seeds (if using). Slice the log into discs, roughly 5mm thick, and arrange on the baking sheets, spacing the biscuits well apart.
Bake on the middle shelf of the preheated oven for 12-15minutes, or until crisp and golden. Once completely cold, the sablés can be packaged.
*Stored in an airtight box, they will keep for 4-5 days.
Gifts from the Kitchen: 100 Irresistible Homemade Presents for Every Occasion by Annie Rigg, published by Kyle Cathie. Recipes and ideas for every season and occasion - from candied almonds and Chinese fortune cookies to slow-roasted tomatoes and macaroons.
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