Steam mussels until they open (approximately 10 minutes). Cool and remove from shells.
Combine garlic, parsley, peppers, lemon zest, butter, and salt in a food processor. Blend until smooth.
Arrange 12 shells on a baking sheet. Place one mussel in each; top with butter mixture and breadcrumbs. Broil until butter melts and breadcrumbs are browned (approximately two minutes).
Optional: serve on bed of microgreens and edible petals.
Three mussels per appetizer serving.