1. Preheat oven to 400 degrees. Spread almonds in an even layer on a baking sheet. Transfer baking sheet to oven and roast until fragrant, about 5 minutes; let cool. Coarsely chop almonds by hand or pulse in a food processor.

2. Place a 5 1/4 quart nonreactive cast-iron roasting pan over medium heat. Add 1 tablespoon butter and cook until melted. Add shallots and garlic, cooking until translucent, 2 to 3 minutes. Add wine and lemon juice, bring to a boil, and immediately remove from heat. Toss in herbs and almonds; season with salt and pepper.

3. Increase oven temperature to 450 degrees. Arrange mussels in the roasting pan in no more than two even layers. Cut remaining 2 1/2 tablespoons butter into pieces and place over mussels. Transfer to oven and roast, tossing mussels to coat, every 3 to 4 minutes, until mussels have opened and sauce is creamy. Serve immediately with bread for dipping.