Rinse the spring onions in cool water and pat dry. Trim the root ends. Separate the stems and leaves, and slice the stems into 3 pieces each. Cut the leaves into pieces roughly the same size as the penne. Place the stems and leaves in a bowl, cover with a damp paper towel, and refrigerate.
Bring the chicken stock to a simmer in a medium saucepan. Season lightly with salt, and keep warm.
Heat ½ cup of the olive oil in a large saucepan over medium-high heat. Add the shallot and sweat until soft and translucent, about 3minutes. Add the penne and toast for 1 minute, stirring constantly with a wooden spatula or spoon.
Add the white wine and bring to a simmer, stirring. Simmer until the wine has almost completely evaporated. Add 1 ½ cups chicken stock and bring to a simmer. Cook, stirring occasionally, for 5 minutes, then add the sauce. Bring back to a simmer, stirring gently from time to time. Slowly add the remaining chicken stock, ½ cup at a tie, cooking and stirring occasionally, as you would risotto, until the penne is al dente and there is still a little cooking liquid in the pan, about 10 minutes total.
Meanwhile, combine the remaining ½ cup olive oil and the thinly sliced garlic in a large sauté pan and heat over medium-high heat. When the garlic begins to sizzle add the tomatoes, season with salt and pepper, andsauté for 3 minutes. Add the spring onions and cook for 1 minute more.
Add the tomatoes and spring onions to the penne. Adjust the heat to medium-high and cook for 2 minutes to allow the pasta to absorb some of the sauce. Season to taste with salt and pepper, add the basil, and serve immediately.