Cook and drain pasta according to instructions on box. Make pasta sauce by combining tomato sauce, paste, water, garlic, onion, italian seasoning (i use penzey's spices) and salt/pepper in a medium sauce pan. Heat on medium-high until sauce starts to simmer aggressively, then lower heat to medium-low, cover, and let it simmer lightly for about 15 minutes, stirring often. Add in the softened cream cheese and sour cream (i used tofutti brand), and heat on low for about 5-10 minutes until you have a nice creamy red sauce.
In a 9x11 glass casserole dish, use about three tablespoons of the sauce to coat the bottom (prevents sticking). Layer 1/2 of the mostaccioli in the dish, then layer 1/2 sauce, 1/2 green pepper and 1/2 of the mozzarella (i used vegan gourmet). Then repeat with the other half of the ingredients.
Pop in the oven at 350 f° for about 25 minutes, until the sauce starts to bubble and the cheese begins to melt. Pull out and cool around 10-12 minutes before trying to serve, although in my house we only make it about 5 minutes.
http://www.thevegancookbook.com [1]