2 cups milk
1 medium onion, finely chopped
5-10 mushrooms, brushed clean and coarsely chopped
1/2 cup Parmesan cheese
2 Tablespoons butter
3 Tablespoons flour
1/2 of a 16oz-can of tomato sauce
In a large saucepan, over medium heat, melt butter and add onions, cooking for 2 minutes. Add mushrooms and continue to cook until onions are translucent, about 4 more minutes. Add milk, reserving some in a glass to make a rue. Add the flour to the reserved milk, whisking until it has dissolved, (the rue) and pour it into your saucepan. Add Parmesan cheese. Reduce heat to medium-low and simmer for several minutes, stirring frequently, so as not to singe the bottom. Add tomato sauce and stir, until color is uniform. Serve over pasta.