In a food processor, process mushrooms until they are no more than ½". Remove into a bowl. In the same processor, process onion and carrot into fine pieces.
Heat butter in a pan, add the processed mushrooms, vegetables and porcini. Cover and cook on medium flame for 5 minutes. Uncover and cook on medium-high flame till the water is evaporated.
Stir in the garlic and cook for 1 minute or until fragrant.
Add the tomato paste and sugar. Cook for 1~2 minutes.
Next add the crushed tomatoes, vegetable stock, salt and pepper; simmer the mixture for 10 minutes.
While the sauce is simmering, cook the pasta until al dente. Reserve ½ cup of pasta cooking water.
Add the pasta sauce to the pasta, mix well and add some pasta cooking water if the mixture looks too dry. Adjust the seasoning and serve with grated with Parmesan cheese and Enjoy!!