Step 1

Place the butter in a medium saucepan, and place over medium heat. Cook until the butter has melted, and then continue to cook, swirling the pan often, until the butter foams and turns golden brown and nutty - this should take 3-4 minutes.

Step 2

Measure out 175g of the brown butter into the bowl of a stand mixer. Allow to cool slightly.

Step 3

Place the bowl of the stand mixer with the brown butter onto the mixer, and fit with the paddle attachment. Mix the brown butter, muscovado sugar, dark brown sugar, and granulated sugar on medium speed until combined. Add the eggs one at a time, followed by the vanilla, then increase the mixer speed to high and beat for 2-3 minutes, until the mixture has lightened in colour and thickened.

Step 4

In a medium bowl, sift together the flour, spelt flour, baking powder, baking soda, and salt. With the mixer off, add to the mixing bowl, then mix on low until just combined.

Step 5

Remove the bowl from the mixer and finish the incorporation of the dry ingredients by hand if needed - scrape down the bowl and ensure that all the mixture at the bottom of the bowl is fully incorporated. Add the chopped chocolate and mix briefly to incorporate.

Step 6

Cover the bowl with plastic wrap and chill for 30 minutes in the fridge. While the dough is chilling, preheat the oven to 350°f/ 180°c. Line 2-3 baking sheets with parchment paper.

Step 7

Using a two tablespoon scoop, place level scoop fulls of dough onto the prepared baking trays - 8 per tray works well for me, but I like to start with 6 just to make sure there will be enough space. Roll each into a ball and arrange on the trays, leaving ample room for spreading.

Step 8

Bake the trays one at a time for 11-12 minutes, or until the cookies are puffed up and set around the edges. Remember that they will continue to cook a little once you remove them from the oven. If the cookies have lost their round shape a little in the oven, you can use a round cookie cutter slightly larger than the cookie to nudge it back into a circular shape. Sprinkle each cookie with coarse sea salt, then cool on the tray for 10 minutes before transferring to a wire rack to cool completely.

Step 9

Repeat the baking process with the remaining cookies. Store leftovers in an airtight container at room temperature.