If using fresh broccoli, blanch it first in boiling, salted water for 1 minute. Drain and let cool before using. Thaw frozen broccoli before using.
In a saute pan over medium high heat, melt the butter. Add the chicken and saute, turning, until it browns on all sides. Add the garlic, broccoli and chicken stock. Let simmer 8-10 minutes. Add the pasta and toss.