Cheddar Oat Seeded Rye Sourdough Boule

Steps

1. Evening before (about 9 pm): feed your sourdough starter at a 1:1:1 ratio of starter, fresh rye flour (medium) from your starter supply and water, so it is ready in the morning; at about 75°F (24°C) it peaks, doubled and bubbly, in 8 to 12 hours.
2. Same evening, make the oat soaker: pour the boiling portion of the water (100 g) over the first portion of the oats (60 g), stir, cover and leave at room temperature overnight.
3. Toast the sesame seeds and the pumpkin seeds together in a dry skillet over medium heat for 3 to 4 minutes until fragrant, then cool. Cube the cheddar and refrigerate it until needed.
4. Morning (about 8 am), once the starter has peaked: in a large bowl, stir the lukewarm portion of the water (320 g) with the sourdough starter until milky.
5. Add the rye flour and the bread flour and mix to a shaggy, sticky dough with a wet hand or spatula; cover and rest 30 minutes.
6. Sprinkle the salt over the dough and squeeze it in. Then work in the oat soaker, the flaxseed, the toasted sesame seeds, the toasted pumpkin seeds and the cheddar cubes until evenly spread. Counting the starter's rye flour and water, the dough is about 68% hydration and 1.8% salt, plus the soaker's water.
7. Bulk rise covered at about 75°F (24°C) for 4 to 5 hours. During the first 2 hours, do 3 sets of gentle stretch-and-folds 30 minutes apart with wet hands. Bulk is done when the dough has risen about 50%, looks domed and shows bubbles at the edges.
8. Turn the dough onto a lightly wetted work surface and shape a round boule with wet hands, building surface tension.
9. Spread the second portion of the oats (20 g) on a plate, mist or brush the top of the boule with water and roll it in the oats to coat.
10. Place the boule oat side down in a parchment-lined bowl or banneton, cover and proof in the fridge overnight, 12 to 14 hours, until slightly puffy and it springs back slowly when poked.
11. Next morning, put a Dutch oven with its lid in the oven and preheat to 475°F (245°C) for 45 minutes.
12. Turn the cold boule onto parchment, score a shallow cross, and lower it into the hot Dutch oven. Bake covered 25 minutes.
13. Uncover, reduce to 450°F (230°C) and bake 20 to 25 minutes more, until the crust is deep brown and crisp and the center reads 205 to 210°F (96 to 99°C).
14. Cool on a rack at least 3 hours before slicing into 12 slices; rye needs this time to set its crumb.