Brown the butter in a light-coloured saucepan over medium heat until foaming, golden and nutty-smelling. Tip into a bowl immediately to stop it cooking further. Cool completely to room temperature, about 20–30 minutes, or 10–15 minutes in the fridge, stirring occasionally.

Beat the cooled brown butter with the granulated and brown sugar for about 2 minutes, until grainy and well combined.

Add the egg yolk and whisk for another 2 minutes, until thickened.

Whisk in the sourdough discard by hand with a balloon whisk.

In a separate bowl, whisk together the flour, cocoa powder, bicarbonate of soda and salt. Fold into the wet mixture just until no streaks remain.

Fold in the dark chocolate chips.

Toss the frozen raspberries in the extra flour or cornstarch, then fold into the dough quickly and gently, straight from the freezer. Don't overmix, a few streaks of raspberry are fine, mashed raspberries are not.

The dough will be soft, that's expected. Don't shape by hand. Use a large cookie scoop (3 Tbsp/45ml) to portion directly onto a parchment-lined tray, aiming for roughly 75g per portion, 8 portions total.

Tidy any portion that needs it with the back of the scoop or a spoon, not your hands.

Freeze the tray uncovered until solid, at least 2 hours. Transfer to an airtight container or freezer bag if freezing longer than a few hours. Can be baked from a 2-hour freeze or held frozen for weeks.

Preheat the oven to 180°C/350°F. Bake straight from frozen for 18–22 minutes, in line with the freeze time and portion size used on the white chocolate raspberry cookie. A cocoa dough won't turn golden the way a plain dough does, judge doneness by a matte, slightly cracked top and edges that feel set rather than soft when nudged, not by colour.

Optional: sprinkle with flaky sea salt as soon as they come out of the oven.

Cool on the tray for 5–10 minutes before moving to a wire rack.