Slice the cooked chicken breasts, against the grain, and get the spaghetti boiling in lightly salted water.
In a large sauté pan, lightly sauté the garlic in the olive oil.
Add the butter, lemon juice and the zest, oregano, wine and Dijon mustard.
Simmer slowly for a minute or two; then add the chopped fresh asparagus and diced red pepper.
Cook for only about 4 to 5 minutes until the asparagus is cooked but still has a little crispness.
Add the sliced chicken, during last minute of cooking, just to warm it through.
Pour the contents of the sauté pan over the cooked spaghetti; toss well before serving.
