In a bowl mix together mustard, thyme, salt and pepper. Sprinkleover both sides of the chicken breasts. Heat oil in a skillet. Add chicken breasts and cook until golden brown. Remove from the pan and slice into strips.
Cook pasta according to package directions. When pasta is cooked melt the butter in a skillet. Add flour and mix well with the butter to combine. Add wine, garlic, onion, and Dijon mustard. Cook about 5 minutes. Reduce heat to low and slowly add milk while stirring. Cook until the mixture begins to thicken. Add cheese and stir it into the sauce until it has melted.
Drain noodles and transfer them to a large serving bowl. Mix in cheddar sauce, add the chicken and toss until well combined.