WHIRL garlic, shallot and jalapeno in a blender or food processor until finely chopped. Add cilantro, parsley, oregano and salt. While whirling, pour 1/3 cup oil and vinegar through spout until puréed. Refrigerate until ready to use. To serve, peel back plastic wrap from terrine. Invert onto a platter, then remove and discard wrap. Cut into 8 slices and drizzle chimichurri sauce on top.