In a large saute pan, heat pan over medium high heat and add olive oil, carrots, onion, celery and mushrooms. Saute until vegetables are tender and lightly browning, approximately 5 minutes.
While veggies are sautéing, stir together your cubed bread with half and half in a small bowl to absorb the liquid.
Next, to your veggies, stir in garlic, sage, rosemary and tomato paste and sauté 1-2 minutes further.
Deglaze pan with two tablespoons dry marsala wine, scraping up any brown bits off the bottom of the pan. Set veggies aside off the heat to cool, about 5-10 minutes.
With a fork, press down your softened bread cubes into the half & half to get a paste-like consistency. Add to a large bowl, discarding any unabsorbed half & half.
Also to the large bowl, add in cooled vegetables, ground beef, egg, salt and pepper.
Use your hands to lightly and minimally mix ingredients until all have just come together, very careful not to overmix.
With your hand, score meat mixture in half, then in fourths. Handling 1/4 at a time, split each into two and form into football-shaped mini meatloaves yielding 8 meatloaves total.
Add to a parchment-lined sheet pan and bake at 400 degrees, for 20 minutes total, rotating 180 degrees midway through. Set aside while preparing gravy.
In your same large saute pan from earlier, add butter and olive oil over medium-high heat and let melt and warm up, 1-2 minutes. Uniformly disperse your sage leaves and let pan fry, about 2-3 minutes per side. Transfer to a paper towel and turn heat down.
To the sage-scented oil mixture, add your sliced mushrooms and garlic. Saute until lightly browned about 5-6 minutes.
Slowly sprinkle your tapioca flour atop mushrooms and stir to absorb. Pour atop beef broth, marsala, salt and pepper and let mixture come to a simmer, while whisking constantly.
When mixture comes to a simmer and begins thickening, add your meatloaves to the pan, spooning your gravy atop.
Serve right out of the pan garnished with crispy sage leaves.