Preheat a water bath to 130°F (54.4°C).
Mix the spices together in a small bowl. Sprinkle the spice mixture over the steak then place in a sous vide bag. Seal the bag and cook for 2 to 4 hours, or up to 24 hours, until heated through or tender.
For more information on the cooking times you can read my detailed article which addresses why is there a range in sous vide cooking times.
Heat some oil in a pan over medium-high heat. Add the onion and cook until beginning to soften. Add the shitake mushrooms, red pepper, garlic and ginger then cook until starting to soften. Add the broccoli, water, soy sauce and lemon juice then cover and cook until tender. Drizzle in the honey and stir to combine. Remove from the heat then salt and pepper to taste.
Add all the ingredients to a blender or food processor and process until it forms a smooth puree. Salt and pepper to taste adding water as needed to thin it out until it is the thickness you desire. It is ready to serve at this point but can benefit from resting in the refrigerator for a few hours for the flavors to fully meld.
Take the sous vide bag out of the water and remove the cooked flank steak. Dry it off thoroughly using paper towels or a dish cloth. Lightly salt the flank steak then quickly sear it for 1 to 2 minutes per side, until just browned, then remove from the heat. Slice the flank steak.
Spoon the vegetable stir fry onto a plate and top with the flank steak. Add a spoonful of the pea pesto, sprinkle with the basil leaves, drizzle with olive oil, then serve.