Rinse fresh PEI Mussels under tap water. Tap any mussels that are still open and discard any that do not close after being tapped and rinsed. Set aside
Place water, bay leaf, onion and the fresh mussels in a large pan over high heat. Cover and steam until mussels open approx 3-4 minutes and steam is coming from under the lid. Using a slotted spoon lift mussels from the pot and place in a bowl. When cool enough to handle, remove mussels from their shells. Discard any that remain closed. Strain the stock, reserving liquid.
Heat olive oil in a large pan over medium heat. Add garlic, onion, carrot and potato and sauté for 5 minutes, stirring occasionally. Stir in curry paste. Add 1 cup reserved mussel stock and reduce by half. Add clam juice, evaporated milk and bring to a simmer.
Spoon a little chowder liquid into a small bowl and add flour. Whisk until smooth then stir mixture back into chowder, stirring to thicken.
Return mussels to chowder and divide between bowls. Garnish with chives and lemon.