What is a vegetarian substitution for pancetta/bacon? Does recipe work if you just omit the meat or can you use something else?

When I write Italian recipes for vegetarians, I often just up the content of olive oil by a couple of tablespoons to take the place of missing pancetta, prosciutto, or other meat. But in this case, the recipe already calls for 4 tablespoons which I think is plenty. If you're truly a vegetarian, you won't be looking for a "meaty" flavor in any case, and if the result doesn't satisfy, you can always dribble a little more well-flavored olive oil on top -- and I'd use a Tuscan oil in this particular case.

Although the recipe uses porcini mushrooms, substituting cubed Portobello mushrooms may work nicely.

I agree with using anchovies to sub for pancetta and/or bacon, but if you don't eat fish, try smoked pressed tofu -- I think Tofu Lin is the best.

Smoked paprika is a good substitute for the smokiness of bacon. It's really tasty but can be strong, so be sure to add it to taste.

The flavor of pancetta and/or bacon adds to a dish what I think is called "umami," which to me means depth of flavor. I find that a good substitute is anchovies and/or herring paste, that is of course assuming that as a vegetarian you eat fish. Try a couple of anchovies in the recipe.

This is not my recipe, but the absence of meat turns it into something other than Bolognese. The classic Bolognese sauce includes a mixture of meats including chicken livers.

Try simmering with a parmigiano reggiano rind or add some grated to the sauce.