Prep the basil: Rinse and dry the leaves well. Excess water can dilute the sauce and mute the color. A salad spinner works best; otherwise, pat dry with a towel.

Toast the pine nuts (optional but recommended): Warm a dry skillet over medium heat. Add pine nuts and stir until golden and fragrant, 2–4 minutes. Let them cool to prevent melting the cheese later.

Start with the garlic and nuts: In a food processor, pulse the garlic and pine nuts until finely chopped. This helps distribute the flavor evenly without over-processing the basil.

Add basil and salt: Add the basil leaves and a pinch of salt. Pulse in short bursts until roughly chopped. Avoid running the machine continuously to keep the mixture from heating up.

Stream in olive oil: With the machine running, slowly drizzle in 1/2 cup of olive oil. Stop and scrape down the sides. If you want a looser sauce, add more oil a little at a time.

Fold in the cheese: Transfer the mixture to a bowl and stir in the grated Parmigiano-Reggiano. Folding by hand preserves a creamy texture and prevents over-processing.

Adjust seasoning: Taste and add salt, black pepper, and lemon juice if using. If it tastes a bit harsh, an extra spoonful of cheese or a splash more oil can round it out.

Serve: Use immediately, or see the storage tips below. For pasta, reserve some hot pasta water and toss with pesto off the heat to create a silky emulsion.