Chicken & mushroom salad w/spicy sesame dressing

125 g/4 oz pack ready-washed salad leaves
one cucumber, sliced diagonal
small handful of chopped fresh mint
4 skinless boneless chicken breasts
12 shitake mushrooms

Dressing
125 ml/4 fl oz (1/2 cup) rice vinegar
1 tsbp/15 ml Dijon dressing
4 tbsp/60 ml rapeseed oil (may substitute canola oil)
2 tbsp/30 ml sesame oil
2 tsp/10 ml soy sauce
4 spring onions, chopped

To make the dressing: Whisk the vinegar and mustard in a bowl. Gradually whisk in both oils, then the soy sauce. Mix in the spring onions. Place the chicken and mushrooms in a large glass baking dish. Pour half the dressing over and turn to coat. Cover and chill for at least 30 minutes. Preheat the grill. Remove chicken and mushrooms from marinade and grill until cooked through about two minutes per side for the mushrooms, about four minutes per side for the chicken. Slice the cooked chicken and halve the mushrooms. Combine the salad leaves, cucumbers and mint in large bowl. Pour remainder of dressing over salad to coat and toss gently. Transfer to individual plates and spoon chicken slices and mushrooms on top.