01 - 
                Preheat oven to 375°F (190°C) and line two baking sheets with parchment paper or silicone baking mats.
              
              
              
                02 - 
                In a medium bowl, whisk together flour, salt, black pepper, and optional smoked paprika.
              
              
              
                03 - 
                In a large mixing bowl, beat together softened butter, shredded cheddar, and Parmesan until well blended. Add egg yolk and cold water, then mix in dry ingredients gradually until a dough forms.
              
              
              
                04 - 
                Scoop tablespoon-sized dough portions, roll into balls, and place on prepared baking sheets 2 inches apart. Press the center of each ball with your thumb or back of a spoon to create an indentation.
              
              
              
                05 - 
                Bake for 10–12 minutes until edges turn golden. Remove and gently press indentations again while still warm.
              
              
              
                06 - 
                Spoon about 1/2 teaspoon of hot pepper jelly into each thumbprint and return to oven for 2–3 more minutes to warm the jelly.
              
              
              
                07 - 
                Let the thumbprints cool on the pan for 5 minutes, then transfer to a wire rack to cool fully. Serve warm or at room temperature.