Place garlic and a pinch of kosher salt in a mortar. Using the pestle, crush and pound the garlic until it forms a smooth, paste-like consistency (about 1-2 minutes).

Add the basil leaves in 3-4 batches, crushing each addition thoroughly before adding more. Continue pounding until all leaves are reduced to a fine, vibrant green paste (approximately 8-10 minutes).

Add pine nuts to the mortar and pound them into the mixture until fully incorporated.

Mix in the freshly grated Parmigiano-Reggiano and Pecorino Romano cheeses, stirring to combine thoroughly.

Gradually drizzle in the olive oil while stirring continuously to create an emulsion.

Taste and adjust seasoning with additional salt if needed.

Transfer to a clean jar and, if not using immediately, cover the surface directly with a thin layer of olive oil to prevent oxidation.