Preheat the oven to 180C / 350F and line three baking trays with parchment paper.
In a medium bowl, sift the flour, bicarbonate of soda, cinnamon, ginger, nutmeg and cardamom.
In a large bowl, beat the butters with an electric whisk until smooth and creamy – this should take about 1 minute. Add your sugars and beat again for 5 minutes until pale, light and fluffy.
Crack your egg into the bowl, along with the vanilla bean paste then whisk again, scraping down the sides of the bowl with a spatula as you go to make sure everything is nicely combined.
Add the oats and continue mixing on a low speed. If you're making the raisin variation, add the raisins too.If you're making the white chocolate variation, add the chopped chocolate too.If you're making the pistachio and cranberry variation, add the chopped pistachios and dried cranberries too.Mix until well combined.
Using a size 20 cookie scoop, form the dough into balls and place them onto your prepared baking sheets, leaving adequate space between each one. N.B. A size 20 cookie scoop is usually about 50-55g of dough if you need to weigh and shape by hand.
Bake one pan at a time in the centre of your oven, turning halfway through the baking time. They should take about 12-14 minutes to bake and be beautifully golden around the edges but lighter and slightly undercooked in the middle. (They'll continue to cook a little while they cool on the baking tray).
Flatten the tops if they've puffed slightly with the back of a frying spatula, then sprinkle immediately with the flaky sea salt and leave to cool completely on the trays.
Notes
These should keep for about three days in an airtight container.