This is our only staple which was invented from scratch (one summer we had more peppers than we knew what to do with). Usually, we start with a published recipe and then it evolves.
Cut hot peppers, remove seeds and white stuff (handle very carefully — I use a knife and fork so I don't have to touch them). When the ingredients in the pot are hot, but not yet boiling, put a few cups in blender, add hot peppers, and blend until very smooth. Pour into big pot. Do another few cups in the blender as a rinse.
Continue to heat until the pot reaches a simmering boil.
Add mushrooms and bring back to a simmer. Cook for 5 to 10 minutes.
In an 8 cup container, melt butter (but don't get it hot) and add flour and stir until smooth (flour blends into butter very easily). Add ½ cup of hot liquid from big pot and stir until smooth. Repeat ½ cup additions until container is full and then add to big pot. Stir for 2 minutes and then turn off heat. There will be enough residual heat to cook the flour. If you were to leave the heat on, there would be burning on the bottom of the pot.
Wait for 10 to 30 minutes. Then ladle a cup or two of the hot liquid into the blender and leave to cool for 15 minutes. Add frozen pesto paste and give it 10 minutes to melt. Add garlic cloves and blend until smooth.
Add this to the big pot after it has cooled for a minimum of a half hour. Run another few cups of the sauce through the blender as a rinse.
Now go to bed because this has taken much longer than you expected. Next day, when it has cooled enough to go into refrigerator, put it there. Then, later, ladle into freezer containers in two-person servings (or whatever is your typical supper number — you may want to do a few singles), leaving enough out for supper. When you heat up this sauce (don't do it more than a few minutes in advance), make it hot but do not boil.