In a large mixing bowl or in a bowl of a stand mixer, combine warm water, yeast, and honey. Let sit for 5 minutes until slightly foamy. Stir in sourdough discard, butter, and salt.
Add flour gradually, mixing until a soft dough forms.
Using a stand mixer and the dough hook attachment, mix on low speed until the dough comes together. Increase to medium-low and knead for 6 to 8 minutes, or until the dough becomes smooth and elastic. It should pull away from the sides of the bowl but still feel soft and slightly tacky. If kneading by hand, turn dough out onto a lightly floured surface and knead for 8 to 10 minutes, until smooth and elastic. If the dough feels very stiff, add 1 tablespoon of water at a time. If it feels overly sticky, add 1 tablespoon of flour at a time.
Place dough in a lightly oiled bowl, cover, and let rise at room temperature for about 1 to 1 ½ hours, or until doubled in size.
Shape the dough into a loaf and place into a greased or parchment-lined loaf pan. Cover and let the dough rise again for 30 to 45 minutes, until the dough crowns just above the pan.
Bake in a preheated oven at 375°F for 35 to 40 minutes, until golden and hollow-sounding when tapped.
Remove from pan and cool completely before slicing.