Corn and Green Chile Enchiladas

1 onion, chopped
2 tablespoons olive or canola oil
Fresh corn, cut from 4 ears
    or 1 package plain frozen corn
1/2 teaspoon whole cumin seed
1/4 cup water salt to taste
1/2 cup sour cream
1 1/2 cups grated Monterey jack cheese
2 (4 ounce) cans chopped green chiles
12 corn tortillas
2 1/2 cups ancho chile sauce or
    2 (10 ounce) cans enchilada sauce

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