Heat olive oil in a large pan or Dutch oven over medium heat. Season the chicken breasts with salt & pepper
Add to the pan and sear for 4–5 minutes per side until golden brown. Remove and set aside. The Chicken does not need to be fully cooked.
In the same pan, add the potatoes- adding a little extra olive oil if necessary.
Add 1 tsp of Italian seasoning. stirring occasionally, until nice and browned. 5-7 min.
Push the potatoes to outside of the pan so that there is room to make the sauce. Make the Dijon cream sauce by Adding 1 tbs of butter and the garlic. Sear for 1-2 min.
Pour in the chicken broth being sure to scrape the brown bits off the pan
Next, add the heavy cream, Dijon mustard and Parmesan cheese. Mix until smooth and slightly thickened.
Return the chicken to the pan, nestling it into the sauce with the potatoes. reduce heat to medium low and Let everything simmer for 15 minutes so the chicken finishes cooking and the flavors come together.
If using, add the broccolini during the last 5-7 minutes of cooking so it becomes tender but still bright.
Spoon the creamy sauce over the chicken and potatoes and serve warm.