Grilled Bigeye Tuna With Israeli Couscous Ragù

Ingredients

• kosher salt
• 1/2 cup Israeli couscous
• 1/4 cup plus 1 tablespoon extra-virgin olive oil
• 1 pound merguez sausage
• 1/4 cup minced garlic
• 1 tablespoon minced shallot
• 1 quart coarsely chopped escarole
• 1 cup shellfish stock
• 5 tablespoons unsalted butter
• 1 tablespoon thinly sliced basil
• 1 tablespoon thinly sliced flat-leaf parsley leaves
• 1 tablespoon minced chives
• freshly ground white pepper
• 1/4 cup Dijon mustard
• 2 tablespoons Colman's mustard powder
• 2 tablespoons thinly sliced cliantro
• 4 Bigeye tuna fillets
• Maldon sea salt