First, peel and quarter the onion. Add it to the mixing bowl and chop for 4 sec / Speed 6.
Scrape down the sides of the bowl with a spatula. Repeat if you prefer a finer chop.
Tear the slice of bread into pieces, add to the onion, and process for 5 sec / Speed 5.
Now add the ground beef, egg, salt, and black pepper, and mix for 1 min / Knead mode.
Stuff the filling into the uncooked cannelloni tubes using your fingers—or for a quick mess-free shortcut, pipe it in using a piping bag! This makes enough filling for about 16 cannelloni tubes.
Arrange the stuffed cannelloni side-by-side in a single layer in a baking dish.
Preheat your oven to 200 °C (400 °F) conventional heat and move on to making the sauce.
Peel the onion and carrots, cut them into rough chunks, and drop them into the mixing bowl. Chop for 5 sec / Speed 5, then scrape down the sides with the spatula.
Wash, seed, and finely dice the red bell pepper.
Add the diced pepper and olive oil to the carrots and sauté for 3 min / 120 °C (250 °F) / Speed 1.
Finally, add the strained tomatoes, heavy cream, sour cream, dried Italian seasoning, sugar, salt, and pepper, and simmer for 6 min / 90 °C (195 °F) / Speed 1.5.
Pour the sauce evenly over the stuffed cannelloni and bake on the lower oven rack for 40 minutes. With 15 minutes remaining, slice the fresh mozzarella, lay it over the top of the pasta, and return to the oven until wonderfully melted and bubbly.
Garnish with fresh basil leaves, serve warm, and enjoy!
Notes
Make sure the cannelloni tubes are completely submerged in the sauce so they bake up nice and tender. Depending on the size of your baking dish, you might need a bit more liquid—if the sauce doesn't quite cover them, just add a quick splash of milk!