1. Make the basil oil: Bring a large pot of salted water to a boil over high heat. Add basil leaves and cook for 15 seconds. Drain and rinse under cold running water; squeeze out excess water. Coarsely chop basil and transfer to the jar of a blender or bowl of a food processor; add olive oil and blend until smooth. Strain through a fine mesh sieve and use immediately or transfer to an airtight container and keep refrigerated for up to 3 days.

2. Make the ricotta spread: Place ricotta in a medium bowl and beat with a fork to make smooth; season with salt and pepper. Stir in radishes, dill, vinegar, and 1 tablespoon basil oil; set aside.

3. Make the tartines: Bring a large pot of water to a boil. Generously salt water and add fava beans and cook for 1 minute. Drain and cool under cold running water. Peel fava beans and set aside. Add peas and asparagus to boiling water; cook for 1 minute and drain. Cool under cold running water, pat dry, and set aside.

4. Spread each slice of toast with ricotta spread. Top with watercress and salmon. Top salmon with asparagus, peas, and fava beans. Drizzle with basil oil and season with a pinch of fleur de sel. Serve.