Hazelnut, White Chocolate and Rosemary Shortbread

Directions

Start by browning the butter. In a small, deep pot over medium-high heat, cook 114 grams (1 stick) of butter, whisking frequently to scrape the bottom of the pot, until it’s a deep honey color and little brown bits form on the bottom of the pot, 4 to 5 minutes. Turn off the heat and allow it to cool in the pot until the solids are a deep brown, about 1 more minute, taking care that they don’t burn. Transfer to a bowl to cool completely and solidify at room temperature. This usually takes about 4 hours, so feel free to brown the butter ahead of time. It should yield 85 grams (3 oz) of brown butter and be the same creamy consistency as the room temperature butter before mixing the dough.When the brown butter is ready, in a mixing bowl cream together the remaining 114 grams (1 stick) of room temperature butter and the brown butter with a wooden spoon or hand beaters. You can also use a stand mixer with the paddle attachment. The mixture should be uniform and smooth. Add the powdered sugar, sourdough starter and vanilla. Mix until fully combined, making sure there are no lumps of powdered sugar.Add the all-purpose flour, rosemary and salt. Switch to a spatula, gently folding together until mostly combined, and then add the hazelnuts and white chocolate chunks, mixing to fully incorporate.

Cover your work surface with a large piece of plastic wrap and turn the dough out onto it. Using your hands, form the dough into a log about 2½ inches (6 cm) in diameter and 12 inches (30 cm) long. The log doesn’t have to be perfect and you can dust your hands with a little flour if it’s sticky. Wrap it in the plastic and roll it back and forth a few times on the countertop to smooth into a cylinder. Transfer to the fridge to chill at least 4 hours or up to overnight. To avoid a flat side on the roll of dough, after the first 20 minutes of chilling, you can take it out and give it a quick reshaping to even out the sides, but I tend not to sweat it.When ready to bake, heat the oven to 325ºF (165ºC) with two racks in the middle third of the oven. Line two sheet pans with parchment paper and set aside. Take the dough out of the fridge and let it sit at room temperature to soften slightly so it slices with ease, about 15 minutes. Dust your work surface evenly with the Demerara sugar and roll the log of dough back and forth over it to coat the outside in a layer of sugar. With a sharp knife cut ½-inch (1-cm)-thick slices and place them on the sheet pans, spaced about 2 inches (5 cm) apart. These cookies don’t spread out much when baked, and you can fit eight to ten cookies on a sheet pan.Bake until just golden on the edges but still pale in the centers, 15 to 20 minutes. Allow to cool for at least 10 minutes on the sheet pans before enjoying.