1. Clean: Scrub the 8 small mussels and 8 medium littleneck clams clean under cold water, then peel and devein the 6 small shrimp.

2. Prep: Peel, seed, and finely dice the 2 large plum tomatoes.

3. Heat: Warm 2 tablespoons of the 4 tablespoons extra virgin olive oil in a heavy pot over medium heat.

4. Steam: Place the cleaned clams and mussels in the pot, cover with a tight lid, and steam for 7 to 10 minutes until the shells open, discarding any shellfish that stay closed.

5. Strain: Drain the steamed shellfish through a fine sieve, reserving the flavorful cooking liquid in a bowl, then remove and discard the shells.

6. Dice: Finely dice the cooked clams, cooked mussels, and raw shrimp, then set the seafood aside.

7. Sauté: Cook 1 clove of the chopped garlic in 1 tablespoon of the remaining olive oil in a skillet over medium heat until fragrant without letting it brown.

8. Simmer: Add the diced seafood, 2 tablespoons chopped Italian parsley, and 1/2 teaspoon crushed red pepper flakes to the skillet and cook for 2 minutes.

9. Reduce: In a separate small pot over medium heat, combine the diced plum tomatoes, 2 tablespoons dry white wine, and the reserved shellfish broth, cooking for 3 to 4 minutes until slightly thickened.

10. Combine: Pour the reduced tomato broth into the seafood skillet, simmer together for 2 more minutes, then remove from the heat.

11. Toast: Rub the 24 slices Italian bread with the remaining 2 cloves garlic, brush with the final 1 tablespoon olive oil, arrange in a single layer on a sheet pan, and toast in the oven or under the broiler on both sides until golden.

12. Assemble: Spoon a generous portion of the warm seafood mixture onto each toasted bread slice, arrange on a serving platter, and serve immediately.

13. Shelf Life: Store leftover seafood topping separately from the bread in an airtight container in the refrigerator for up to 1 day, and reheat gently before spooning onto freshly toasted slices.

14. Serve: Arrange the warm seafood crostini on a platter and pass immediately.