This is great vegetarian streetfood which tastes great made at home.
Puree the beans, garlic, lemon juice, 30 millilitres of the oil and the zest in a food processor or mash all together well.
Stir in the chives, taste and season. Reserve.
Heat a barbecue or ridged grill (or frying pan) over moderate to high heat.
Brush the remaining oil over the blanched asparagus and the mushrooms, season with salt and pepper and barbecue, grill or fry for about 4 minutes on each side until well browned.
Spread the insides of the buns with the bean puree and place some watercress, some asparagus, a mushroom and some feta on each of the bottoms.
Place the tops of the buns on the filling and serve.
1 can Cannellini Beans drained
1 Garlic Clove peeled and chopped
300 millilitres Lemon Juice
75 millilitres extra virgin olive oil
Zest of 1 lemon
10 grams chives, finely sliced
300 grams asparagus spears woody ends snapped off, blanched in a saucepan of boiling water for 2 minutes
250 grams large mushrooms, stalks sliced off flush with the caps
4 hamburger buns, sliced in half, insides toasted under the grill
50 grams watercress sprigs, thick stems discarded
100 grams Feta sliced