Prepare pie crust mix according to package directions; divide into 6 equal balls and roll out each 1-inch larger than inverted tart plate or pan.
Line six 6-inch tart plates or pans with the pastry; flute edges (press points firmly over edge of plates) and prick bottom and sides with fork.
Bake as directed.
Remove from oven and set aside on wire rack.
Reduce oven temperature to 350°F.
Cook onion in hot oil in a large skillet until transparent.
Add ground beef and sausage and cook over medium heat, cutting apart with a fork or spoon, and pouring off fat as it collects.
Remove from heat.
Sprinkle meat with salt, monosodium glutamate, seasoned pepper, and chili powder.
Combine boiling water and milk; stir in potato flakes and continue stirring until soft.
Lightly mix potatoes into meat.
Stir in a blend of egg, evaporated milk, and chili sauce.
Mince 2 pimientos and mix in with the green pepper.
Cut remaining pimientos into 12 triangles.
Lightly spoon meat mixture into baked shells.
Cover tops of tarts with alternating triangles of pimiento and cheese; place a mushroom half in center of each tart.
Brush tops generously with cooking oil.
Set in 350°F oven 8 to 10 minutes, or until mix- ture is thoroughly heated.