Preheat oven to 300°F and line two baking trays with parchment paper.

Using electric beaters or stand mixer fitted with paddle attachment, whip butter on its own on medium-high speed until fluffy. Add icing sugar and beat in, starting on low and then increasing to medium-high, until light and fluffy, 2 to 3 minutes. Beat in vanilla. Add flour, potato starch and salt and blend on low speed until dough comes together. Stir in mini chocolate chips.

Use small mechanical scoop to portion cookies; if scoop is larger than size of cookie you want (just larger than a toonie), scoop dough and then cut each portion in half. Roll each cookie portion into a ball between the palms of your hands and place on baking tray, leaving 1½ in (4 cm) between them. Use fork dipped in flour to press each cookie down (or use a cookie stamp, if you have one).

Bake cookies for about 30 minutes. They will show a touch of light browning on the bottom but should not be brown otherwise. Cool cookies on their trays on racks before packing in airtight container.