Put the chicken breasts on a board and cover with a sheet of baking parchment. Use a rolling pin or meat mallet to bash to an even thickness of about 2cm, being careful not to break the chicken into pieces.
Combine the lemon zest, crushed garlic, olive oil and some seasoning in a medium bowl, then add the chicken and turn in the marinade to coat. Transfer to the fridge while you make the pesto.
Toast the flaked almonds in a dry frying pan over a medium heat for 2-3 mins, shaking the pan often until the almonds are golden brown. Tip into a small food processor or blender. Peel the whole garlic clove and tip this into the food processor along with the parsley, basil, most of the mint leaves, the parmesan, extra virgin olive oil and lemon juice. Season, then blitz to a fine texture.
Cook the orzo in a large pan of boiling salted water following the pack instructions, or until al dente. Heat a griddle pan over a medium-high heat and cook the marinated chicken for 4-5 mins on each side until cooked through with char lines. Drain the orzo and transfer the chicken to a plate to rest.
Drizzle the asparagus spears with a little extra virgin olive oil and season with salt, then griddle for 3 mins until just softened. Remove from the heat and set aside.
Toss most of the pesto through the cooked orzo along with any resting juices from the chicken. The remaining pesto will keep covered in the fridge for up to five days. Slice the chicken breasts. Tip the orzo onto a large serving platter and pile the asparagus and chicken on top, then scatter with the remaining mint leaves, some parmesan shavings and a grinding of black pepper. Drizzle with a little extra virgin olive oil and serve warm.