Place parsnips and potatoes in a large saucepan and cover with water. Bring to a boil over high heat, then reduce heat to medium and simmer, partially covered, for about 13 minutes or until tender when pierced with a knife. Drain parsnip mixture, then return to pot and cook over medium heat for 1 minute to remove any moisture.
Mash parsnip mixture until smooth, then stir in 1/2 cup of the yogurt, butter, 1/2 teaspoon of the salt and 1/8 teaspoon of the pepper until well blended. Cover and keep warm.
Sprinkle pork with chicken grill seasoning. Cut pork crosswise into 1 1/2-inch-thick steaks.
Heat 1 tablespoon of the olive oil in a large nonstick skillet over medium heat. Add pork to skillet, cut-side down, and cook for about 10 to 12 minutes total, turning pieces until all sides are lightly browned and internal temperature reaches 145 degrees. Reduce heat to medium-low if pan gets too hot.
Remove pork from skillet and heat remaining 1 tablespoon oil in skillet. Add shallot to pan and cook, stirring for 2 minutes. Stir in flour and cook 1 minute, stirring often. Slowly whisk in broth, remaining 1/4 teaspoon salt and 1/8 teaspoon pepper and boil for 3 minutes or until slightly thickened. Remove pan from heat and let cool 10 minutes; whisk in remaining 1/4 cup yogurt. Serve sauce with pork and parsnip mixture.