Method

• 1.
  Melt butter with garlic and tarragon in a saucepan over low heat. Remove from heat and set aside for 1 hour to infuse. Pass through a sieve and discard solids.
• 2.
  Place the marron in the freezer for 30 minutes (this will put them to sleep).
• 3.
  Bring a large saucepan of water to the boil over high heat, then add 1 tsp salt. Blanch the marron for 30 seconds or until pale orange. Remove and set aside until cool enough to handle. Twist to remove heads and discard. Using scissors, cut along the belly and remove the shell. Discard shell and set aside meat.
• 4.
  Heat a barbecue or chargrill pan over high heat. Brush cos with oil and season. Grill, turning, for 2-3 minutes until charred.
• 5.
  When ready to serve, place the infused tarragon butter in a saucepan over medium heat until the butter reaches 100°C. Add marron tails, then remove from heat and set aside for 5 minutes to poach.
• 6.
  Remove marron from pan and divide among plates. Combine radish, grilled lettuce and salad leaves in a bowl, then add to plates. Drizzle over poaching butter, then squeeze over lemon juice and dot with mayonnaise.