Preheat the oven to 375F

melt 2 tbsp butter in a large pan on medium, add the cabbage and 2 tbsp garlic with a generous amount of salt, stir to combine and saute til the cabbage begins to soften, but still retains some crunch- about 10 minutes. Remove from heat and set aside

Add the cabbage, meat and cheese to a bowl and toss with a spoon til fully combined.

Stuff the shells with the filling and place them in a 13x9" baking dish, open side up

In a separate pan melt 3 tbsp butter on medium-high. Add the onions and tomatoes and saute for about 2 minutes til softening and fragrant

stir in the mustard, garlic, thyme, and oregano and saute another 1-2 minutes until fragrant

Add the broth and tomatoes, reduce the heat to medium-low, then stir in the cream and parmesan

Cover the pot, bring the heat back to high until simmering, then reduce to low and simmer for 4 minutes

Blend the sauce with an emulsion blender or regular blender

poor the blended sauce evenly over all the shells, cook in the oven on the center rack at 375F for 10-15 minutes, then broil for 1-2 minutes

Remove the shells from the oven, garnish evenly with fresh basil and serve