Grilled Pierogies and Kielbasa

1 pound kielbasa (pork or turkey), cut into 4 pieces
2 tablespoons whole-grain mustard
2 tablespoons apple cider vinegar
1/4 cup extra-virgin olive oil
1 large white onion, cut into 6 wedges
1 pound potato-and-cheddar pierogies
Kosher salt and freshly ground pepper
1/4 cup roughly chopped fresh parsley

Use homemade pierogie recipe from previous post.
 
Preheat a grill to medium. Grill the kielbasa, turning, until marked, 8 to 10 minutes. Transfer to a platter.
Meanwhile, whisk the mustard and vinegar in a large bowl. Slowly whisk in 2 tablespoons olive oil until smooth.
Toss the onion and pierogies with the remaining 2 tablespoons olive oil and season with salt and pepper. Saute`uncovered, until the pierogies are browned and the onion begins to soften, about 5 minutes. Turn the pierogies and onion and continue to saute`, until the pierogies are cooked through and the onion is tender, 4 to 6 more minutes. Transfer to the platter.
Slice the kielbasa into pieces and add to the bowl with the mustard dressing. Roughly chop the onion and add to the bowl along with the pierogies and parsley. Season with salt and pepper and toss. Divide among shallow bowls.  Good Eating!!