This is one of the “secret ingredients” of the cooking of the Catalonia region of Spain—not really a sauce, and never served by itself, but a condiment to be stirred directly into stews, soups, and sauces a few minutes before they are finished cooking. Picadas destined to be used with meat, poultry, or game dishes often include a bit of chocolate; those to be used with fish sometimes have fish roe or livers added.
Heat in a small skillet over medium heat:
      1 tablespoon extra-virgin olive oil
Add and brown:
      1/2-inch thick slice French bread or Italian bread
Crumble and place in a mortar or small food processor or blender. Pound with a pestle or process along with:
      1/2 cup whole blanched almonds, skinned hazelnuts, and pine nuts, or all almonds, coarsely chopped and toasted
      2 cloves garlic, halved
      8 black peppercorns (optional)
      Salt to taste
      Pinch of toasted saffron threads (optional)
Remove the mixture to a bowl and thoroughly work in with a fork:
      3 tablespoons extra-virgin olive oil, or as needed
      1 teaspoon finely chopped fresh parsley
Let stand until the picada holds together in a thick paste, about 30 minutes. The picada will keep, covered and refrigerated, for up to 2 days.