To prepare the salmon glaze, in a small bowl, mix together Dijon mustard, horseradish sauce, and honey until well combined.
Rub olive oil on both sides of salmon fillets and season with salt and pepper.
Light a grill under medium high heat and grill salmon, skin side down, for about 3 minutes. Turn then grill for an additional 3 minutes, until salmon is almost cooked through. Turn salmon and spread glaze on top. Let heat for about 30 seconds and turn once more. Glaze that side of salmon and grill for about 30 seconds longer. (At this point, the salmon is perfect to eat as is also!) Transfer to a plate and tent with foil.
To prepare the hash, in a large pot of salted water, bring the potatoes to a boil. Bring heat to medium high and let cook for about 15 minutes, or until they are starting to become tender. Drain the water and carefully peel the potatoes (I would use a napkin to hold the potatoes because those suckers are gonna be hot!). Cut the potatoes into a small dice and set aside.
In a large skillet, cook the bacon until starting to crisp, about 5 minutes or so. Transfer to a napkin-lined plate with a slotted spoon and set aside.
Add 2 tablespoons of olive oil to same large skillet used for bacon. Add the diced potatoes and cook over medium high heat for about 10 minutes, or until they are starting to brown. Cover the skillet and let cook under low heat for about 10 minutes, or until tender.
Add onions and apples to potatoes. Cover and cook for about 7-10 more minutes, or until apples start to become tender. Quickly chop the salmon into decent sized pieces and stir into mixture. Cover and cook for 2 to 4 more minutes, or until salmon is warmed. Stir in bacon and remaining glaze if you have some left over. Season with salt and pepper, if needed and serve with a fried egg on top!