Instructions

Adjust oven rack to upper-middle position and heat oven to 450 degrees. Lightly crumple 26-inch length of aluminum foil into loose ball. Uncrumple foil and use to line rimmed baking sheet.
Melt 2 tablespoons softened unsalted butter in 12-inch nonstick skillet over medium heat. Add ¾ cup panko bread crumbs and cook, stirring occasionally, until panko is golden brown, 2 to 5 minutes. Add 3 minced garlic cloves and 1 tablespoon minced thyme and cook until fragrant, about 30 seconds. Off heat, add ¼ cup minced parsley and stir to combine; transfer panko mixture to plate and set aside. Wipe skillet clean with paper towels.
Line fine-mesh strainer with coffee filter and set over bowl or large measuring cup. Combine 36 littleneck clams and ½ cup white wine in now-empty skillet. Cover and cook over medium-high heat, shaking pan occasionally to redistribute, until clams just open, 4 to 10 minutes. Using tongs, transfer clams to large bowl as they open (discard any unopened clams). Set aside until cool enough to handle, about 15 minutes. Strain clam broth through prepared strainer. Set aside ½ cup broth (if you have less than ½ cup, add enough white wine to equal ½ cup). Rinse and wipe skillet clean with paper towels.
Cook 6 chopped slices bacon in now-empty skillet over medium heat until lightly browned but not crispy, 7 to 10 minutes. Stir in ½ cup finely chopped green bell pepper and 2 minced shallots and cook until softened, 2 to 5 minutes. Add ½ cup reserved broth. Bring to vigorous simmer and cook until liquid is nearly evaporated, 3 to 5 minutes. Transfer mixture to bowl and refrigerate until completely cooled, about 15 minutes.
Remove clam meat from shells using paring knife or your clean hands. Separate joined clamshells. Arrange half of shells on prepared sheet, pressing each shell into foil to keep shell level (discard remaining shells). Place 1 clam into each shell.
Add remaining 8 tablespoons softened butter to cooled bacon mixture and mash with fork until combined. Using 2 spoons, evenly distribute butter mixture among clamshells (about 2 scant teaspoons each). Spread butter mixture evenly over each clam.
Divide panko mixture evenly over each buttered clam (about 1 teaspoon each), pressing lightly to adhere. Roast clams until butter has melted and crumbs are deep golden brown, about 5 minutes. Serve immediately with lemon wedges.TO MAKE AHEAD: Cooled panko mixture, prepared through step 2, can be stored in airtight container overnight. Buttered clams, prepared through step 6 and covered with plastic wrap, can be refrigerated for up to 24 hours; proceed with step 7, increasing total roasting time to 6 to 8 minutes.