Fill a large pan with water for boiling the spaghetti.  Add the slice of onion, 2 whole garlic cloves, salt and bay leaves.  Boil for 2 minutes, then add the spaghetti and cook according to the package directions.  This is usually about 8 to 10 minutes.  Taste a piece of spaghetti to see if it is fully cooked. Discard the onion, garlic and bay leaves.

Remove the spaghetti from the water, and reserve ½ cup of the spaghetti water.

Preheat the broiler to 500°.  Place the poblanos, skin side up on the cookie sheet on the highest rack directly under the broiler.  Broil till the skins are blackened and bubbled, between 3 and 5 minutes.

Remove and place in a bag to steam for 5 minutes.  Remove and peel the skins off.  Cut into strips.

In a large pan, melt the butter and add the olive oil to heat.  Add the grated onion and garlic and sauté for 3 to 4 minutes. Add the sliced poblanos and sauté for an additional 5 minutes.

Place the cilantro, cream cheese, chicken bouillon, cream, milk, and poblanos in the blender.  Blend till smooth, then pour into the pan and cook for 5 to 10 minutes until very smooth.  If the sauce gets too thick, add some of the reserved spaghetti water to the sauce.

Add the spaghetti and toss to coat.  Serve with a sprinkle of queso fresco and some chopped cilantro.