Cheese and Spinach Pierogi

Ingredients

• 1.1 pounds all-purpose flour
• 1 cup hot water
• 2 tbsp unsalted butter (at room temperature)
• ¼ tsp salt
• 1 tbsp unsalted butter
• 1 shallot (diced)
• 1 garlic clove (minced)
• 3 1/2 ounces spinach ((optional))
• ½ tsp black pepper
• 1.1 pounds boiled potatoes
• 3 1/2 ounces grated cheddar
• 3 1/2 ounces grated Gruyère
• 3 1/2 ounces grated Emmental
• ½ tsp dried marjoram
• 2 tbsp unsalted butter
• 1 tbsp olive oil
• 7 ounces bacon bits
• 1 yellow onion (cut into thin slices)