Bring large pot of water to a boil. Add some salt to water. Cook pasta according to package directions until al dente.
Meanwhile, heat olive oil in a large pot. Add garlic and onion, and saute until softened. Add clams, wine and clam juice. Cover and cook until clams open. Remove clams as their shells open and reserve.
Add butter and cream to clam sauce. Season with black pepper. Add al dente pasta to sauce and toss well. Stir cornstarch slurry mixture and add to sauce. Toss pasta in sauce and cook until sauce thickens.
Divide pasta and sauce among serving bowls. Top with cooked clams. Squeeze lemon juice on top. Sprinkle basil on top.