Prepare Your Ingredients - Bring a large pot of salted water to boil for the pasta. While waiting, grate your pecorino cheese finely and beat the eggs in a medium bowl. Add most of the grated cheese to the eggs, reserving some for garnish. Cut your pancetta alternative into small cubes.

Cook the Protein - In a large skillet over medium heat, cook the pancetta alternative until crispy and golden brown. If using garlic, add it during the last minute of cooking. Remove from heat but keep the skillet warm.

Cook the Pasta - Cook the spaghetti according to package directions until al dente. Reserve about 1 cup of pasta water before draining. The starchy water is crucial for creating the perfect sauce consistency.

Combine Everything - Working quickly, add the hot drained pasta to the skillet with the pancetta. Toss to coat. Remove from heat entirely and let cool for 30 seconds. Pour the egg and cheese mixture over the pasta, tossing continuously to create a creamy sauce. Add pasta water as needed to achieve your desired consistency.

Final Touches - Season generously with black pepper and additional salt if needed. The sauce should be creamy and smooth, coating every strand of pasta. Serve immediately with extra cheese and parsley garnish.