Heat the oven to 400°F. Line baking sheets with baking paper.
Put the flour, salt, cayenne, and baking powder in a food processor. Pulse to combine. Add the butter and pulse again until the butter is in small pieces, six to eight 1-second pulses. Add the cheeses, pulse, and finally, add the egg and pulse until the mixture just starts to come together.
Tip the dough on an unfloured surface. Knead by lightly smearing the ingredients together as you push them away from you with the heel of your hand until the dough is cohesive.
Shape the dough into logs roughly 2 inches in diameter and wrap in film and chill for a couple of hours, until firm.
Take the logs out of the fridge, remove film and brush with egg and paprika and coat with the sesame and cumin seeds. Slice the log in to disk about 1/8 of an inch high.
Arrange the disks on the lined baking trays spacing well. Bake in the oven for 12 to 15 minutes. To test, break one in half and look to see if the center still looks doughy. If so, cook for a few more minutes, but be careful not to overbake. Let cool on a rack and store only when completely cool.
Keep a couple of extra logs in the freezer. Slice and bake when guests pop by! I also like to add cheddar or blue cheese and nuts.