Combine onion, carrot, 1 garlic clove and 1 1/2 tsp. olive oil in heavy medium saucepan. Cook over low heat until veggies are tender, stirring frequently, about 8 minutes. Add curry powder and saute 2 minutes. Add stock and rosemary and bring to a boil. Reduce heat to medium and cook until reduced to 2 1/2 cups, about 25 minutes. Strain through sieve set over bowl, pressing on solids. Heat remaining 1 1/2 tsp. olive il in heavy large nonstick skillet over medium-low heat. Add mushrooms and cook until almost no liquid remains in skillet, stirring frequently, about 10 minutes. Increase heat to medium-high. Add shallot and remaining minced garlic and saute 5 minutes. Add strained stock and boil until liquid is reduced to 2 cups, about 10 minutes. Transfer to blender and blend until smooth, about 2 minutes. Strain through a sieve, set over a saucepan. Mix in lemon juice. Season to taste with pepper. (Can be prepared one day ahead. Cover and refrigerate.) Bring sauce to a simmer, mix in tarragon and serve. Serve over grilled pork, veal or chicken.