Remove the stem from strawberries. Add to a Ziploc bag and mash.
Remove the stems from jalapeños and add to a food processor or blender and pulse to break up.
Add butter to the pan. Once melted, add the jalapeños, brown sugar, and red pepper flakes and cook until softened, about 4 minutes.
Add remaining ingredients to the saucepan and stir. Bring to a boil, stirring often.
Once mixture starts to boil, reduce heat to a simmer and cover. Simmer for 15 minutes.
Remove from heat. Let sit covered for 5 minutes.
Pour into jars and allow to cool completely.
Refrigerate overnight before serving.
Notes
Taste before jarring: Adjust the spice or sweetness to your liking before cooling. Use gloves for jalapeños: Protect your hands when handling spicy peppers. Let it chill overnight: This helps the flavors fully develop and the texture firm up. Use sterilized jars: For longer storage, make sure your jars are clean and dry.