Using a mortar and pestle or a cutting board and the flat side of a knife, crack the coriander seeds. Add to a large dry saucepan over medium heat and toast for 1 minute, or until fragrant.
Add butter and wine to the coriander in the pan, and swirl until butter has melted, about 2 to 3 minutes.
Add shrimp, lemon juice and pinch of salt. The liquid should come about halfway up the sides of the shrimp. If needed, add a splash more wine to the pan.
Gently poach shrimp for 2 minutes, then flip. Poach for another 1 to 2 minutes, or until they turn pink and are just cooked through.
While shrimp are poaching, make the dill mayonnaise: In a small bowl, whisk together lemon zest and juice, dill, mayonnaise and salt. Taste, and add more salt and lemon juice if needed.
Pour shrimp and all of their juices into a shallow bowl, and top with dollops of dill mayonnaise. Garnish with dill fronds and serve.