Saute mushrooms in hot butter until they are crisp and browned, then stir in garlic and stir fry for 2 minutes; stir in the tomatoes and set aside.
Now, make pastry: Mix flour and salt in bowl, then cut in butter and shortening with a pastry cutter until crumbly.
Add milk, one tablespoon at a time; mix lightly until all is moistened; add more milk if necessary.
Gather in a ball and roll out between 2 sheets of wax paper, peel off one sheet, place pastry onto 8 or 9-inch pie plate and peel off 2nd sheet; fit nicely into shell and crimp edges; paint edges with small amount of unbeaten egg white.
Or, if you don't want to make pastry, use a prepared crust and paint edges as above.
Now make custard: Beat together the whipping cream, egg yolks and spices; stir in basil.
Now fill unbaked pie shell with mushroom mix, then pour custard over.
Bake in a preheated 375F oven for 40 to 45 minutes, until custard is set and deeply browned.