Wash your buckwheat in a pot, gently rinsing and draining to get rid of extra starch/impurities.
Transfer to a sieve for a final rinse, before bringing back to the saucepan. Heat the saucepan on a low heat to gently toast the buckwheat for 1-2 minutes, bringing water to a boil in a kettle in the meantime.
Add 1 and a 1/2 cup of hot water to the saucepan, add salt and mix, turning the heat up to medium to bring to a gentle boil. Wash and slice mushrooms, then add in the pan, once bubbling, cover and simmer for 15-20 minutes or until water is absorbed.
Remove the pan from the heat and wash your salad veggies. Slice cherry tomatoes into quarters, cucumber into slices and pepper into smaller strips. Dice your red onion and thinly cut bunched lettuce, then set your salad ingredients aside.
In a small bowl, add tahini, lemon juice, agave syrup, seasonings, salt and iced water, combining with a whisk. If the mixture is too thick, add a little more water a tsp at a time/more tahini if too runny, you should get a nice drizzly texture.
In a large salad bowl, combine the cooled buckwheat and prepped salad veggies. Toss and mix well with salad tongs, then drizzle in the tahini dressing, a crack of black pepper, and a final toss.
Serve and enjoy immediately, or cool in the fridge for later. Can be kept for up to 4 days airtight in the fridge.