In a large bowl, whisk together the water, brown sugar, and yeast. Cover and let sit for 10 minutes to activate the yeast.
Once the yeast is bubbly and foamy, add the melted butter, 2½ cups flour, and salt. Stir together until combined and the flour is well incorporated. You want the dough to be tacky, but not sticky. If the dough is wet and sticky, stir in more flour a spoonful at a time (up to ½ cup).
Turn the dough out onto a lightly floured surface and knead for 5 minutes.
Cover and let rest for 30 minutes.
Meanwhile, preheat the oven to 400°F and line a large baking sheet with parchment paper. Fill a large pot with 2 quarts of water and whisk in ¼ cup baking soda. Turn on the water bath to boil.
Divide the dough into 6 equal pieces. Shape each piece into an 18-22" rope. You may need to do this in two stages, if the dough resists stretching past a certain point. Cover the ropes and let them sit for 10 minutes, then continue rolling them out to the desired length.
Shape the ropes into hearts. Working one rope at a time, form a V. Then bring both ends down and in to meet above the point of the V in a heart shape. Press the ends together to seal. Cover until the water bath is ready.
Gently transfer one pretzel to the water bath and cook for 10 seconds. Remove the pretzel from the bath and place it on a wire rack. Sprinkle with a pinch of coarse salt. Repeat with the remaining pretzels.
Place the salted pretzels on the parchment-lined baking sheet.
Bake for 15 minutes until golden brown. Serve warm with mustard for dipping.
Notes
Storage: Store covered at room temperature for up to 3 days, or in the freezer for up to 3 months.Pretzel bites: Skip the shaping and make pretzel bites. To make pretzel bites, simply use a knife or bench scraper to cut each rope into 2-inch pieces. Place up to 10 bites into the water bath at a time. Salt and bake as directed. Makes 50-60 pretzel bites.Honey mustard dip: ¼ cup mayonnaise + 3 tablespoons yellow mustard + 1 tablespoon honey + 1 pinch saltHot mustard dip: ¼ cup mayonnaise + 3 tablespoons yellow mustard + 1 tablespoon hot sauce + ¼ teaspoon cayenne pepper + 1 pinch salt