Heat half of the olive oil over medium-high heat in a large skillet or wok (see Recipe Note #4). Add the kielbasa coins in a single layer across the bottom. Brown well on both sides (~2–3 minutes per side). Remove to a bowl or plate (preferably one you'll be eating out of so you don't dirty an extra dish!).
Reduce the heat to medium. Add the remaining olive oil to the pan (do not wipe it out). Add the onions and fennel. Sauté until the vegetables are translucent and soft (5–7 minutes), scraping any browned bits off the bottom of the pan. Add the garlic, salt, pepper, and spice mix. Sauté for an additional minute.
Mix in the cabbage, mustard, and chicken broth. Lid the skillet and let the cabbage steam, stirring occasionally, until soft, 5–8 minutes.
Add the kielbasa back to the skillet and stir to combine. Taste the cabbage to check the seasoning, adjusting as necessary. Serve and enjoy.