To Be Frank Melt-In-Your Mouth Buttery Shortbread

1. Read through the full recipe, including the tips below before starting. We like our cookies to crumble, not fall apart half-way through.
2.  Preheat the oven. Set your oven to 300 °F fan / 325 °F conventional. Low and slow is the secret here — it gives the cookies their melt-in-the-mouth texture without coloring too much on top.
3. Cream the butter. Fit Ooni Halo Core with the Angled Silicone-Edge Beater attachment. Beat 225 g unsalted butter at 50-60% (5-6 fully lit segments on dial) speed for 3–4 minutes, until very pale and fluffy. Don't skip this step — the air you're beating in right now is what makes the final cookie so light.
4. Add the sugar and vanilla. Lower speed to 40% speed (4 fully lit segments on the dial) and add 90g powdered sugar, a spoonful at a time, beating as you go. Add 1 tsp vanilla extract and mix until everything is smooth and creamy.
5. Add the flours. Add 200g all purpose flour, 60g cornstarch and a pinch of salt all at once and mix at 10% (1 fully lit segment on the dial) until the dough just comes together. Stop as soon as you can't see any more dry flour — overmixing will make the cookies tough.
6. Shape and chill. Lightly flour a surface and roll the dough out to about 1 cm thickness. Cut into rectangles of roughly 6×3 cm. If using demerara sugar to coat, lightly toss each piece in now. Place on a lined baking tray with a little space between each cookie. Refrigerate for 20–30 minutes — this helps them hold their shape in the oven. 
7. Move tray to oven. Bake for 20–22 minutes until pale golden and completely firm in the middle. They will still feel slightly soft when hot — that's fine. They firm up as they cool. 
8. Cool and enjoy. Leave to cool completely on the tray before moving. They'll firm up to that perfect crumbly texture as they cool — resist the urge to eat them straight away (or don't, we won't judge). 

Tips

• Room temperature butter is key. Cold butter won't cream properly. If you've forgotten to take it out, cut it into small cubes and leave for 20–30 minutes before starting.
• Cornstarch is the secret. The combination of plain flour and cornstarch gives these cookies an extra-fine, melt in your mouth crumb.
• Don't doubt the temp. 300°C feels low, but it's what gives these cookies their pale golden color and delicate snap. A hotter oven will brown them too fast.
• They keep well. Store in an airtight container at room temperature for up to 1 week. They taste even better on day 2 once the butter has settled.
• Using these as a cheesecake base? Bake them fully, cool completely, then blitz in the mixer until you have fine crumbs. Mix with a little melted butter and press into your springform pan.