Gently pull the stamen out of each blossom and pinch off the tough green sepals at the base. Wipe each one clean with a damp paper towel rather than rinsing under water, since they bruise fast.

Tear half the blossoms into 2 to 3 strips and set the rest aside whole.

Steep the saffron threads in 2 tbsp of warm broth for 5 minutes, then set aside.

Heat the vegetable broth in a 2.8 L saucepan and keep it at a bare simmer, about 85 C / 185 F, on a back burner.

Melt half the butter with the olive oil in a 30 cm / 12-inch pan over medium heat. Add the shallot and cook 3 to 4 minutes until soft and translucent, not browned.

Add the rice and stir to coat in the fat. Toast for 2 minutes, until the grains look glassy at the edges and smell nutty.

Pour in the wine and stir until fully absorbed, about 1 to 2 minutes.

Stir in the saffron broth, then begin ladling in hot broth one ladle at a time, stirring often and waiting for each addition to absorb before adding the next. Continue for 16 to 18 minutes total.

At the 10-minute mark, fold in the torn blossom strips so they melt into the broth and tint it pale gold-green.

Taste the rice at 17 to 18 minutes total. It's done when it's al dente with a slight bite in the center and the risotto spreads slowly when you tilt the pan.

Remove from the heat. Stir in the remaining butter, parmesan, and mascarpone vigorously for 30 seconds until glossy.

Fold in the reserved whole blossom pieces gently so they keep some shape. Cover and rest off heat for 2 minutes, then season with salt and pepper and plate.