Heat a large soup pot over medium high heat and add oil. Stir in shallot and cook for 1 minute. Add sprigs of herbs, garlic and mustard seeds. Add mussels, stirring once, then cover and let cook 1 minute. Add wine and immediately cover. Cook mussels until all are opened, about 3 minutes. Remove herb sprigs and pull out any mussels that have not opened.
Season lightly and stir in butter and parsley.
Spoon mussels into a large serving bowl (or serve in pot) and serve immediately.
For the Flatbread (makes 4):
Combine flour, crushed coriander seeds, baking powder and fine salt in a bowl. Stir in yogurt until dough comes together, then turn out onto a clean, lightly floured surface and knead just until dough feels elastic, about 3 minutes. Return dough to bowl, cover with plastic and let rest for 30 minutes.
Divide dough into 4 equal pieces, and roll each piece out into an oval about 8-inches long. Heat a cast iron skillet over medium heat and melt 1 Tbsp butter, until foaming subsides. Add 1 flatbread to skillet and cook until bubbles and spot turn brown, about 4 minutes. Turn flatbread over and continue to cook until the same browning occurs. Remove flatbread onto a baking tray and repeat with remaining flatbreads.
Immediately before serving, warm flatbreads in a 300 °F oven for 5 minutes. Melt remaining 2 Tbsp butter and brush flatbreads. Sprinkle with salt and chopped fresh coriander and serve immediately.
Notes & Tips
Alternatively, flatbreads can be grilled over medium-high, for about 4 minutes on each side.