Saute garlic in oil over medium heat to release flavor. Do not brown. Add onions and continue to saute until onions become translucent. Add tomatoes, jalapenos, green chiles, chicken cubes, chili powder, cumin, mexican oregano, and salt. Bring to boil, lower heat and simmer for 10 to 12 minutes. Set filling aside.
Fry tortillas in vegetable oil, over medium high heat, just long enough to make soft and flexible. Do not allow to crisp. Remove to paper towels and cover until ready to assemble enchiladas.
Heat half and half with bouillon cube. Do not boil. Gradually add 4 oz shredded monterey jack cheese and whisk until smooth. Dip tortillas into cheese sauce. Place 2 to 3 T of the chicken mixture along with 1 T of each grated cheese on each tortilla and toll up.
Arrange seam-side down in a greased 13 inch baking pan. Pour remaining cheese and bake, loosely covered at 350 degree oven for 30 minutes. Garnish with sliced scallions and salsa.