Start by grating your butter on the coarse side of a cheese grater. This will help incorporate the butter quickly and easily.
In a large bowl, mix together the flour, baking powder, baking soda, garam masala and salt. Add the grated butter and using your fingertips, swiftly rub the flour and butter together to form a fine, breadcrumb-like texture.
Add the onion, chilli, coriander and cheese. Mix together.
Next, pour in the milk. Use a spoon or your hands to bring the mixture together as a soft dough. Be very gentle and do not knead it. Light and flaky scones require as little handling as possible.
Flour a clean surface and pat or roll the dough out to a thickness of about 1 1/2-2cm. Stamp out rounds using a cookie cutter. Pick up any scraps of dough and bring them back together to cut out more rounds. Remember to handle the dough quickly and with a light touch. Cracks on the surface are fine. Scones should be rustic looking.
Place the scones on a large baking tray lined with baking parchment. Arrange the scones on the tray, leaving a small gap around each one as they will rise a bit. Refrigerate for 5 minutes.
To make the mustard "eggwash":
In a small bowl, mix together the mustard and milk. Stir until no lumps remain.
To bake the scones:
Brush the scones with the mustard wash and sprinkle on your kalonji (nigella) seeds and sesame seeds. Alternatively, you can keep them plain or choose an alternative. I've included some different topping ideas in the blog post above.
Bake the scones in the pre-heated oven for 20-22 minutes. Allow to cool for 15-20 minutes before eating.
Serve these scones with Masala Chai and if you like, mango chutney. I sometimes like to add a blob of whipped cream cheese and mango chutney together, cream tea style.
Cut the scones into any shape you like. Note that larger scones may take longer to bake.
Store the scones in an airtight container, somewhere cool. Enjoy within 2 days. Refrigeration may make the scones stale.