In a small pot, bring chicken stock to a simmer.
Meanwhile, heat oil in a large pot over medium heat. Add shallots; sweat until translucent, about 1–2 minutes. Add asparagus to the pot and cook for 3 minutes, stirring occasionally. Pour chicken stock into the pot and continue cooking for another 3 minutes or until asparagus is tender. Transfer to a high-power blender and add 1 cup ricotta. Purée until smooth. Season with salt and lemon juice. Divide soup among 4 bowls.
Combine remaining ¼ cup of ricotta and truffle oil in a small mixing bowl. Top each cup of soup with a tablespoon of the ricotta mixture and garnish with a sprig of dill. Serve immediately.