While water comes to a boil, heat a deep skillet over medium heat.
Add extra-virgin olive oil and butter.
To warm oil and butter add crushed red pepper flakes, garlic and shallots, saute 3 minutes, add shiitake mushrooms and cook until tender, 3 to 4 minutes more.
Deglaze the pan with sherry or Marsala wine, scatter in crabmeat - feeling for shell bits as you go.
Warm the ingredients through, a minute or so, stir in tomatoes and heat through, 2 to 3 minutes.
Stir in half-and-half or cream and reduce heat to lowest setting.
Drain pasta when cooked to al dente and toss with sauce and crab.