Step 1
Soak porcini in 2 cups boiling water for at least 10 minutes.
Step 2
At the same time heat olive oil in a medium Dutch oven over medium heat. Add shallot and slowly saute until soft and juices have been released 3 to 5 minutes.
Step 3
Remove porcini from the water and use a damp paper towel to remove any grit. Reserve soaking water.
Step 4
Add porcini to the Dutch oven with miso paste and yeast extract. Stir well and reduce heat to a simmer.
Step 5
Add broccoli; put floret heads facing down and stem pieces nestled in so they are touching the bottom of the pot. Layer radicchio slices evenly on top. Pour in wine without disturbing the vegetables. Cover and simmer occasionally shaking the pan gently for 10 minutes.
Step 6
Meanwhile bring 2 cups water vegetable broth and salt to a boil. Sprinkle fistfuls of polenta into the boiling liquid while stirring constantly so clumps don't form. Continue to stir in polenta until completely added. Reduce heat to low and cook stirring often until polenta is thick and cooked through about 10 minutes.
Step 7
Strain the reserved soaking water twice if necessary to remove any sediment.
Step 8
Pour 1/2 of the soaking water into the Dutch oven with the broccoli. Gently shake the pot and use a wooden spoon to carefully loosen the florets without breaking them apart. Gently fold vegetables over until coated with cooking sauce. Continue to simmer uncovered occasionally shaking the pot. Cook until broccoli is tender but still firm to the touch and radicchio is completely wilted. Season with salt and pepper.
Step 9
Pour polenta onto a lightly oiled polenta board and spread it evenly over the board. Use a slotted spoon to gently spoon vegetables over the polenta.
Step 9
Pour remaining soaking water into the Dutch oven and bring to a boil. Make a slurry with the remaining water and cornstarch; pour into the Dutch oven while whisking constantly. Cook until sauce has thickened 2 to 3 minutes. Pour sauce over the broccoli and polenta or serve on the side.