To steam the crab, bring 1 to 2 inches of water to a boil in a pot that is wide enough and deep enough to accommodate a whole crab. Place the crab in a steamer basket in the pot, cover and steam for 15 to 20 minutes. Cool.
Remove meat from shell. Place meat aside and reserve the leg shells for stock.
For crab stock, combine all ingredients and bring to a boil, reduce heat and let simmer for 30 minutes. Drain and return the stock to the stovetop on low heat.
Chop cauliflower. Blanch until very tender. Puree with heavy cream. Set aside.
In another large pot, sweat the shallots in olive oil, add the rice; continue to stir until very lightly toasted.
Add Tom Gore Vineyards Chardonnay and continue to stir. Let it reduce by three-quarters of the way.
Add crab stock 1 cup at a time; each time letting it reduce by half way. Continuously stirring throughout the entire process. Risotto will be done when rice is cooked through. (Depending on your rice you may not use all the liquid.)
Remove from heat and stir in butter, cauliflower puree, and pulled crab meat.
Lightly toss purslane in lemon juice and garnish risotto. Serve.