HEAT OIL IN A DUTCH OVEN, OVER A MEDIUM FLAME ADD ONIONS, HEAT AND STIR FOR 2 MINUTES ADD GARLIC AND MINCED CHILES, HEAT AND STIR FOR 4-5 MINUTES ADD GROUND BEEF, CU MIN, AND OREGANO HEAT AND STIR TO BROWN BEEF ADD CHILE POWDER, TOMATO CONCASSE, AND WATER BRING TO A BOIL, REDUCE HEAT, AND SIMMER FOR 2-1/2 TO 3 HOURS, STIRRING OFTEN COMBINE INSTANT MASA AND 2 TABLESPOONS WATER-MIX WELL ADD TO CHILI MIXTURE, HEAT AND STIR UNTIL THICKENED SLIGHTLY REMOVE FROM HEAT GARNISH WITH GRATED CHEESE AND MINCED SCALLIONS SERVE HOT