Mash the anchovy and garlic together using a pestle and mortar, then tip the mixture into a bowl and whisk in the mustard, buttermilk, lemon zest and juice, and season with black pepper. Put the kale and peas in a large bowl, pour over ¾ of the dressing, then massage into the kale so each leaf is coated.
Put the chicken thighs between two pieces of baking parchment, then bash out with a rolling pin to 1cm thickness.
Heat a griddle pan until searing hot. Brush the bread slices with a little oil, then griddle until lightly charred on all sides. Set aside.
Next, season the broccoli and brush the cut side of each piece with a little oil. Griddle, cut-side down, in batches for 3-4 mins until tender. Lastly, brush the remaining oil over the chicken thighs and season, then griddle the chicken for 3-4 mins on each side until cooked through.
Distribute the kale between four plates. Slice the chicken diagonally and break the bread into pieces. Top each of the plates with ¼ of the chicken, broccoli and croutons. Grate over the parmesan in large shavings and drizzle with the remaining dressing to serve.