Summarize:

Pour 1 tbsp oil into your pan and heat it until it starts to shimmer. Use 1/2 of a fresh medium onion, diced. You can use a white, yellow, or purple onion. Any one will taste great, so use your favorite kind or whatever you have on hand. Stir your onions frequently and cook them in the oil for about 5 minutes or until they turn translucent. Be careful adding the fresh onion, once your oil has heated up, it may pop and sizzle when you pour the onion into the pan. Peel and dice two garlic cloves and cook with the onions for another minute. Garlic is delicious and has great health benefits, but it is also very strong in flavor. If you are sensitive to garlic, just add one clove or half a clove. Drop in 1 can of drained and diced green chilies, and 1 lb of green tomatoes or tomatillos, roughly chopped. You can use fresh green chilies too. Add 1 tsp cumin, 1/2 tsp oregano, 1/2 tsp salt, 1 cup vegetable broth and 1/2 cup water to the skillet. Many store bought broths have preservatives and additives so you may be better off making your own vegetable broth. Bring your sauce to a boil and then reduce the heat to a simmer and cook for about 10 minutes, stirring occasionally. Your tomatoes should start to break down, giving your sauce a thicker and richer consistency. This is a great time to get creative with your sauce. Taste it as it heats up and add an additional pinch of salt or oregano if you desire. At this point, you are ready to pour your sauce onto a dish of freshly assembled enchiladas. Just sprinkle with 1/2 cup of cilantro and use it immediately or store it in an airtight container in the refrigerator for later. You can adjust the amount of cilantro to your taste.
Heat the vegetable oil in a large nonstick skillet over medium heat. Pour in the onion. Add the garlic. Pour in your chilies. Spice it up! Cook your sauce. Remove from heat.