Preheat oven to 450°F. Line a baking sheet with parchment paper. Set aside.
Cook sausage in a large skillet over medium heat until no pink remains, around 5-8 minutes. Drain grease from pan and set aside to cool.
In a large mixing bowl, use a whisk to sift together flour, baking powder, salt, ground mustard and baking soda.
Add grated butter, stir with a fork until evenly distributed.
To the bowl add sausage, cheese and chives, stir together to combine.
Make a well in the center of the flour mixture, add buttermilk. Stir thoroughly. Turn out onto a lightly floured non-stick surface. Turn a couple of times to bring together and lightly coat with flour.
Press into roughly a 9x9-inch square around 1-inch thick. Use a sharp knife dipped in flour to cut into 12 even squares.
Place squares side by side on baking sheet. Brush tops with melted butter or heavy cream.
Bake for 18-20 minutes or until golden brown and puffy.
Serve immediately brushed with additional melted butter, if desired.