Preheat your grill to medium-high heat and your oven to 425°F for roasting the broccoli.
Season the chicken breast with salt, pepper, and a light dusting of garlic powder.
Grill the chicken breast for about 6-7 minutes per side, or until the internal temperature reaches 165°F.
While the chicken cooks, toss the broccoli with half of the olive oil, salt, and pepper; spread evenly on a baking sheet and roast in the oven for 15-20 minutes until tender and lightly charred.
For the cauliflower mash, steam the cauliflower florets until very tender. Transfer to a bowl, add the remaining olive oil and skim milk, then mash until smooth. Season with salt, pepper, and a pinch of garlic powder.
Toast one slice of sourdough bread if desired.
Plate the grilled chicken alongside the roasted broccoli and a generous serving of cauliflower mash, with the toasted sourdough on the side.