Step 1: Toasted Breadcrumbs: In a medium skillet over medium heat, add 2 tablespoons of olive oil. Once shimmering, add the breadcrumbs. Cook, stirring frequently, until they are golden brown and crispy, about 5-7 minutes. Season with a pinch of salt and pepper. Remove from the skillet and set aside in a bowl.
Step 2: Cook the Pasta: Bring a large pot of heavily salted water to a rolling boil. Add the spaghetti and cook according to package directions until al dente. Before draining, reserve 1.5 cups of the starchy pasta water.
Step 3: Infuse the Oil: While the pasta cooks, in the same skillet (no need to clean it) over medium-low heat, add the remaining 1/4 cup of extra virgin olive oil, sliced garlic, and red pepper flakes (if using). Cook gently for 5-7 minutes, stirring occasionally, until the garlic is fragrant and barely golden. Do not let it burn!
Step 4: Combine: Using tongs, transfer the al dente spaghetti directly into the skillet with the garlic-infused oil. Add 1/2 cup of the reserved pasta water. Toss vigorously to combine, allowing the pasta to absorb the sauce and the starches to emulsify, creating a slightly creamy consistency.
Step 5: Adjust Consistency: Continue adding pasta water, a splash at a time, and tossing until the sauce coats the spaghetti beautifully and reaches your desired consistency. The sauce should be glossy and slightly thick, not watery.
Step 6: Final Seasoning: Taste and adjust seasoning with salt and freshly ground black pepper.
Step 7: Serve: Divide the Spaghetti Aglio e Olio among serving plates. Garnish generously with the toasted breadcrumbs and fresh parsley, if desired. Serve immediately.