Mix the dry ingredients together in a bowl (that is, flour, salt, baking powder and cinamon).

In an electric mixer, mix the butter and sugar until pale and fluffy. (This can be done manually, just keep mixing until the butter and sugar mix changes colour and becomes fluffy).

Beat in the eggs and vanilla.

Reduce the speed of the mixer and gradually add in the flour mixture. Mix until just combined.

Using plastic wrap, form dough into logs and chill for about four hours (until firm).

Cut enough 1/8- to 1/4-inch-thick slices from log with a heavy knife to fill 2 ungreased large baking sheets, arranging slices about 1 inch apart.

Bake cookies, then switch position of sheets halfway through baking, until edges are golden, 12 to 15 minutes total. Cool on sheets 3 minutes, then transfer with a metal spatula to racks to cool completely. Make more cookies with remaining dough on cooled baking sheets.