In a large saute pan on medium-high heat, with olive oil quickly caramelize the onions and garlic. Once browned add inmushrooms and further caramelize.
Once the mushrooms are golden brown add in the arborio rice and toast for 3 to 4 minutes, then deglaze with the madeira wine and cook until the rice absorbs the wine.
To make the risotto add in one 4 ounce ladle of chicken stock one at a time until the rice has absorbed all the of the liquid while constantly stirring.
While the rice is cooking place 2 saute pans on high heat each one with 1/2 ounce of butter. Once the butter is melted add the mussels and clams to one pan and the shrimp and lobster to the other pan.
Saute for 3 to 4 minutes and then deglaze with the chardonnay wine. The steam from the wine should open up the mussels and clams. NOTE: if the clams or mussels do not open simply add more wine until they do.
Once all the clams and mussels are open and the lobster and shrimp are just done add all seafood to the risotto pan.
Finish the risotto with the tarragon, parmesan cheese, cream and adjust the seasonings with salt and pepper.