In a small saucepan, bring cream, dried mushrooms and garlic to a boil. Remove from heat and let cool. In the bowl of a food processor, purée bread, onion, 1 egg and cream mixture. Add meat and pulse a few seconds at a time until smooth. Season with salt and pepper.
Place flour on a plate and 2 eggs in a second shallow dish. Season with salt and pepper and beat lightly. Place breadcrumbs in a third dish.
Shape patties with about 75 ml (1/3 cup) of meat mixture. Give them an oval shape and flatten slightly. Dredge patties in flour and then dip in eggs. Shake off any excess, then press in breadcrumbs to coat well. Set aside on a large plate.
In a large non-stick skillet over medium heat, heat oil. Brown a couple of patties at a time, about 5 to 6 minutes per side, or until cooked through. Drain on paper towel. Keep warm. Repeat with remaining croquettes, adding oil as needed.
Meanwhile, in large skillet, brown mushrooms in half the butter. Add remaining butter and cook over medium to low heat until tender, about 10 minutes. Season with salt and pepper.
Serve patties with sautéed mushrooms and Pierogis (see recipe).