Preheat the oven to 350°F (for later). Also, begin with bringing a medium pot filled with at least 5 inches of water to a boil, on the stove.
Once the water boils, carefully add the chopped broccoli florets and cook 2 minutes.
Use a slotted spoon to transfer the broccoli to a large bowl filled with ice water. Allow to chill in the ice water for 1-2 minutes, before transferring broccoli to a paper towel to dry.
Once broccoli is no longer wet, transfer to a large bowl and set aside for later use.
Meanwhile, add 1 tablespoon olive oil to a frying pan and turn the heat to medium. Add ⅓ of the sliced mushrooms and arrange in an even layer. Cook 2 minutes before flipping each mushroom or simply mixing and cooking another 2 minutes until golden on both sides. Transfer cooked mushrooms to a plate and sprinkle with a pinch of salt.
Repeat the mushroom cooking process with the remaining 2 batches of mushrooms, so that each batch can cook in an even layer. Add more oil between each batch if needed.
Once mushrooms are cooked use the same frying pan to toast the pine nuts over a medium-low heat, about 2 minutes. Remove from the pan immediately once golden so that they don’t burn.
Set aside mushrooms and pine nuts to cool completely.
Meanwhile, toast the walnuts in the oven for 5 minutes until fragrant. Once cooked + cooled, chop into medium pieces.
Make the dressing by whisking together all the dressing ingredients in a medium bowl. Alternatively, use a blender to prepare the dressing.
Combine the blanched broccoli, pan-seared mushrooms, pine nuts, chopped walnuts, yellow pepper & red onion to a large bowl. Mix together.
Pour all the dressing over the salad ingredients and toss until combined.