Preparation

• Line two large rimmed baking sheets with parchment. In a medium saucepan, melt the butter over low heat; keep warm.
• In the bowl of a stand mixer fitted with the paddle attachment, combine the flour, cacao nibs, sugars, cocoa, cardamom, and salt. Mix on low speed until combined, about 30 seconds. With the mixer running, slowly pour in the butter. Stop the mixer as soon as the butter is incorporated, about 1 minute. The streusel will appear moist but crumbly.
• Divide the streusel between the prepared baking sheets, spreading it to cover the
  entire pan and breaking up any large clumps with your fingers. Refrigerate for at least 30 minutes or overnight. Use right away, or transfer to a zip-top bag and freeze airtight for up to 3 months.