Broccoli, Cauliflower and Avocado Salad

1 1/2 pounds tender broccoli
1 1/2 pounds cauliflower
1 avocado
2 T fresh lemon juice
1/2 cup chopped pecans
1 T Dijon mustard
1/4 cup light olive oil
Salt to taste
Remove broccoli  and cauliflower florets from large stems.  Peel avocado and cut into cubes.  Combine avocado and 1T lemon juice in small bowl to prevent darkening.  Add broccoli and cauliflower and pecans to bowl.  Stir together 1 T lemon juice, mustard and salt until combined.  Add oil and blend.  Pour over salad and toss and serve.  I will usually mix all and add avocados as I serve it. That way it can be refrigerated over night and add avocados when ready to serve.