Combine hocks, wine, garlic, thyme and parsley stalks in a saucepan, add 2.5 litres cold water, bring to the simmer over medium-high heat, then reduce heat to medium, cover and simmer until meat is almost falling from the bone (1-1¼ hours). Remove hocks from liquid (reserve liquid), then when just cool enough to handle, coarsely shred (discard skin, bones and sinew) and place in a bowl. Add shallot and vinegar, season to taste and stir to combine.
Strain 750ml cooking liquid into a saucepan and simmer over medium-high heat until reduced to 300ml (40-45 minutes). Pour onto ham mixture, stir to combine, cool to room temperature, stir in parsley then transfer to sterilised jars or ramekins, pressing firmly to smooth top. Refrigerate until set then cover. Persillade will keep refrigerated for 2 weeks. Serve with baguette, cornichons and mustard.