First, make the marinara sauce
In a large frying pan, add olive oil and about half of the crushed garlic. Cook for a minute until fragrant..
Add the peppers and onions. Stir well and cook on high heat for a few minutes until they start to brown. Then reduce heat to medium-low and continue to cook for about 10 more minutes. While the onions and peppers are cooking, add in a little of the tomato juice from the can. This will ensure they soften while they cook and not burn
Add can tomatoes, herbs, salt and pepper. Continue to cook until the liquid in the tomatoes reduces by half. This will take around 30 minutes. Stir as it cooks. At this point taste your sauce and see if it is bitter at all. If so, add about a teaspoon of sugar. Stir well and leave to simmer for a few more minutes.
Once you have finished this, add the mixture to the blender and blend in batches until you have a smooth sauce. Flavours can be adjusted once you have made your sauce with additional herbs, salt, pepper, sugar....
Heat the reserved skillet and add a little olive oil and garlic. Add mushrooms and cook until browned, about 5 minutes.
Then add in chicken to the mushrooms. Cook just to brown the chicken for a about 3 - 4 minutes. Remove from heat. Add prepared sauce and the fresh spinach to the chicken and mushroom mixture. Stir well
Cook pasta in boiling water for 8 minutes. Remove and instantly rinse with cold water. Let drain.
To assemble the lasagna you need a large lasagna pan. Put a tiny amount of sauce on the bottom layer. This is just so the pasta does not stick. Then you can start layering. First a layer of lasagne sheets, followed by a few ladles of sauce, few spoonfuls of sour cream and finally cheese. Keep repeating the process until all layers are done. I usually get around 4 layers.
Bake in a preheated oven of 350 degrees for around 40 minutes. Remove from oven and let stand for 10 to 15 minutes. This allows time for the lasagna to set so when cut it stays together.
Can be served with any fresh salad and garlic bread. Makes for great, fuss free entertaining as it can be made ahead and refrigerated up to 24 hours before baking.