Prepare the vegetables:

Trim the woody ends off the asparagus and cut the rest diagonally in half.
Blanch the asparagus in salted water for 2–3 minutes, then rinse under cold water.
Do the same with the peas (1 minute for fresh, slightly longer for frozen).

Start the risotto:

Heat the olive oil in a wide pan. Sauté the shallot over medium heat for about 3 minutes until translucent.
Add the rice and stir for 1 minute until the grains become glossy.

Deglaze and add garum:

Pour in the white wine and let it reduce almost completely.
Add the mushroom garum and stir to combine.

Add the stock gradually:

Add a ladleful of hot stock and let it simmer, stirring frequently.
Once absorbed, add another ladle. Continue this process until the rice is al dente (about 18–20 minutes).

Add the vegetables:

In the final 3 minutes of cooking, add the blanched asparagus and peas to warm through.

Finish the risotto:

Remove the pan from the heat. Add the butter, Parmesan, and lemon zest.
Stir well and let the risotto rest, covered, for 2 minutes.

Serve:

Spoon the risotto into deep plates. Top with watercress and a twist of black pepper.