Step 1Place the bread in a food processor and pulse until it forms rough crumbs, some fine and some the size of peas. You should get about 1 1/2 cups. Place a quadruple-thick layer of paper towels on a plate and keep nearby.
Step 2Heat the oil in a large skillet over medium-high heat until the oil begins to shimmer. Add the crumbs (they will look sodden in the oil; it’s OK) and cook, stirring, until light brown, 3 to 4 minutes. Add the shallots, peanuts, ginger, garlic, salt, ground peppercorns, chile flakes and sugar, and continue cooking, stirring, until everything is golden brown and crisp, 4 to 5 minutes more. Immediately scrape everything in the skillet onto the paper-towel-lined plate and spread out in an even layer to cool.
Step 3While the crumbs cool, arrange the cucumbers in on a platter large enough to fit them in a single-ish layer. Drizzle the cucumbers with the soy sauce and vinegar, then cover them with the breadcrumbs, letting a few of the points and peaks stick out on top. This is best served when the cucumbers are still cold from the fridge and the crumbs are warm, but it will still taste great as it sits and comes to room temperature.