Set a large skillet over medium heat with 1 tablespoon butter. Once melted, add in the chicken. Season with a large pinch of salt, pepper and paprika. Cook until browned, about 8 to 10 minutes. You don't have to worry about cooking it through all the way as it'll continue to cook later on. Use a slotted spoon to remove the chicken onto a plate and set aside.
Add another tablespoon of butter to the skillet and then add the shallot and garlic. Cook until softened, about 2 to 3 minutes. Stir in the mushrooms and continue to cook until browned and just beginning to crisp. Season with another pinch of salt and pepper.
Add the remaining 2 tablespoons of butter. Once melted, sprinkle the flour over the top and cook for about 30 seconds or so to remove that raw flour taste. Stir in the chicken stock and reduce the heat. Return the chicken to the skillet and simmer until the chicken has cooked through and the sauce has thickened, about 5 to 8 minutes. Give it a taste and adjust seasoning accordingly.
Meanwhile, lay the bread slices onto a baking sheet in a single layer. Drizzle with the olive oil and place under the broiler until golden brown and crispy. Flip over and brown the second side.
To assemble, set a browned bread slice on a plate and then spoon over the stroganoff over the top. Dollop with sour cream and garnish with parsley and paprika. Serve immediately and enjoy!